diff --git a/exercises/error_handling/errors5.rs b/exercises/error_handling/errors5.rs
index eb5506c..6da06ef 100644
--- a/exercises/error_handling/errors5.rs
+++ b/exercises/error_handling/errors5.rs
@@ -4,7 +4,7 @@
 
 // This exercise uses some concepts that we won't get to until later in the course, like `Box` and the
 // `From` trait. It's not important to understand them in detail right now, but you can read ahead if you like.
-// For now, think of the `Box<dyn ???>` type as an "I want anything that does ???" type, which, given
+// For now, think of the `Box<dyn ...>` type as an "I want anything that does ???" type, which, given
 // Rust's usual standards for runtime safety, should strike you as somewhat lenient!
 
 // In short, this particular use case for boxes is for when you want to own a value and you care only that it is a
diff --git a/exercises/functions/functions1.rs b/exercises/functions/functions1.rs
index 03d8af7..38c3538 100644
--- a/exercises/functions/functions1.rs
+++ b/exercises/functions/functions1.rs
@@ -1,8 +1,10 @@
 // functions1.rs
 // Execute `rustlings hint functions1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
     call_me();
 }
+
+fn call_me() {
+    println!("I'm Nidhal Messaoudi, a software developer going Rusty!!!");
+}
diff --git a/exercises/functions/functions2.rs b/exercises/functions/functions2.rs
index 7d40a57..5a51bdf 100644
--- a/exercises/functions/functions2.rs
+++ b/exercises/functions/functions2.rs
@@ -1,13 +1,11 @@
 // functions2.rs
 // Execute `rustlings hint functions2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
     call_me(3);
 }
 
-fn call_me(num:) {
+fn call_me(num: i32) {
     for i in 0..num {
         println!("Ring! Call number {}", i + 1);
     }
diff --git a/exercises/functions/functions3.rs b/exercises/functions/functions3.rs
index 3b9e585..5b2a9a1 100644
--- a/exercises/functions/functions3.rs
+++ b/exercises/functions/functions3.rs
@@ -1,10 +1,8 @@
 // functions3.rs
 // Execute `rustlings hint functions3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
-    call_me();
+    call_me(12);
 }
 
 fn call_me(num: u32) {
diff --git a/exercises/functions/functions4.rs b/exercises/functions/functions4.rs
index 65d5be4..40677fc 100644
--- a/exercises/functions/functions4.rs
+++ b/exercises/functions/functions4.rs
@@ -7,14 +7,12 @@
 // in the signatures for now. If anything, this is a good way to peek ahead
 // to future exercises!)
 
-// I AM NOT DONE
-
 fn main() {
     let original_price = 51;
     println!("Your sale price is {}", sale_price(original_price));
 }
 
-fn sale_price(price: i32) -> {
+fn sale_price(price: i32) -> i32 {
     if is_even(price) {
         price - 10
     } else {
diff --git a/exercises/functions/functions5.rs b/exercises/functions/functions5.rs
index 5d76296..52b8400 100644
--- a/exercises/functions/functions5.rs
+++ b/exercises/functions/functions5.rs
@@ -1,13 +1,11 @@
 // functions5.rs
 // Execute `rustlings hint functions5` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
     let answer = square(3);
     println!("The square of 3 is {}", answer);
 }
 
 fn square(num: i32) -> i32 {
-    num * num;
+    return num * num;
 }
diff --git a/exercises/if/if1.rs b/exercises/if/if1.rs
index 587e03f..660a093 100644
--- a/exercises/if/if1.rs
+++ b/exercises/if/if1.rs
@@ -1,13 +1,16 @@
 // if1.rs
 // Execute `rustlings hint if1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 pub fn bigger(a: i32, b: i32) -> i32 {
     // Complete this function to return the bigger number!
     // Do not use:
     // - another function call
     // - additional variables
+    if a > b {
+        a
+    } else {
+        b
+    }
 }
 
 // Don't mind this for now :)
diff --git a/exercises/if/if2.rs b/exercises/if/if2.rs
index effddbb..1fca9c3 100644
--- a/exercises/if/if2.rs
+++ b/exercises/if/if2.rs
@@ -4,13 +4,13 @@
 // Step 2: Get the bar_for_fuzz and default_to_baz tests passing!
 // Execute `rustlings hint if2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 pub fn foo_if_fizz(fizzish: &str) -> &str {
-    if fizzish == "fizz" {
+    if fizzish == "fuzz" {
+        "bar"
+    } else if fizzish == "fizz" {
         "foo"
     } else {
-        1
+        "baz"
     }
 }
 
diff --git a/exercises/intro/intro1.rs b/exercises/intro/intro1.rs
index cfc55c3..5488977 100644
--- a/exercises/intro/intro1.rs
+++ b/exercises/intro/intro1.rs
@@ -9,8 +9,6 @@
 // when you change one of the lines below! Try adding a `println!` line, or try changing
 // what it outputs in your terminal. Try removing a semicolon and see what happens!
 
-// I AM NOT DONE
-
 fn main() {
     println!("Hello and");
     println!(r#"       welcome to...                      "#);
diff --git a/exercises/intro/intro2.rs b/exercises/intro/intro2.rs
index efc1af2..b5b1d0a 100644
--- a/exercises/intro/intro2.rs
+++ b/exercises/intro/intro2.rs
@@ -2,8 +2,6 @@
 // Make the code print a greeting to the world.
 // Execute `rustlings hint intro2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
-    println!("Hello {}!");
+    println!("Hello {}!", "World");
 }
diff --git a/exercises/iterators/iterators1.rs b/exercises/iterators/iterators1.rs
index f9cc3b3..0379c6b 100644
--- a/exercises/iterators/iterators1.rs
+++ b/exercises/iterators/iterators1.rs
@@ -10,7 +10,7 @@
 
 // I AM NOT DONE
 
-fn main() {
+fn main () {
     let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];
 
     let mut my_iterable_fav_fruits = ???;   // TODO: Step 1
diff --git a/exercises/macros/macros4.rs b/exercises/macros/macros4.rs
index 4ee9803..c1fc5e8 100644
--- a/exercises/macros/macros4.rs
+++ b/exercises/macros/macros4.rs
@@ -3,7 +3,6 @@
 
 // I AM NOT DONE
 
-#[rustfmt::skip]
 macro_rules! my_macro {
     () => {
         println!("Check out my macro!");
diff --git a/exercises/quiz1.rs b/exercises/quiz1.rs
index dbb5cdc..9988f9d 100644
--- a/exercises/quiz1.rs
+++ b/exercises/quiz1.rs
@@ -10,10 +10,20 @@
 // Write a function that calculates the price of an order of apples given
 // the quantity bought. No hints this time!
 
-// I AM NOT DONE
-
 // Put your function here!
-// fn calculate_price_of_apples {
+fn calculate_price_of_apples(quantity: i32) -> i32 {
+    let mut quantity= quantity;
+    if quantity <= 40 {
+        quantity = quantity * 2;
+    }
+    return quantity;
+
+    // if quantity > 40 {
+    //     quantity
+    // } else {
+    //     quantity * 2
+    // }
+}
 
 // Don't modify this function!
 #[test]
diff --git a/exercises/smart_pointers/arc1.rs b/exercises/smart_pointers/arc1.rs
index ffb306a..93a2703 100644
--- a/exercises/smart_pointers/arc1.rs
+++ b/exercises/smart_pointers/arc1.rs
@@ -32,7 +32,7 @@ fn main() {
     for offset in 0..8 {
         let child_numbers = // TODO
         joinhandles.push(thread::spawn(move || {
-            let sum: u32 = child_numbers.iter().filter(|&&n| n % 8 == offset).sum();
+            let sum: u32 = child_numbers.iter().filter(|n| *n % 8 == offset).sum();
             println!("Sum of offset {} is {}", offset, sum);
         }));
     }
diff --git a/exercises/smart_pointers/cow1.rs b/exercises/smart_pointers/cow1.rs
index 885138a..5fba251 100644
--- a/exercises/smart_pointers/cow1.rs
+++ b/exercises/smart_pointers/cow1.rs
@@ -4,9 +4,6 @@
 // Cow is a clone-on-write smart pointer.
 // It can enclose and provide immutable access to borrowed data, and clone the data lazily when mutation or ownership is required.
 // The type is designed to work with general borrowed data via the Borrow trait.
-//
-// This exercise is meant to show you what to expect when passing data to Cow.
-// Fix the unit tests by checking for Cow::Owned(_) and Cow::Borrowed(_) at the TODO markers.
 
 // I AM NOT DONE
 
@@ -23,52 +20,29 @@ fn abs_all<'a, 'b>(input: &'a mut Cow<'b, [i32]>) -> &'a mut Cow<'b, [i32]> {
     input
 }
 
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn reference_mutation() -> Result<(), &'static str> {
-        // Clone occurs because `input` needs to be mutated.
-        let slice = [-1, 0, 1];
-        let mut input = Cow::from(&slice[..]);
-        match abs_all(&mut input) {
-            Cow::Owned(_) => Ok(()),
-            _ => Err("Expected owned value"),
-        }
+fn main() {
+    // No clone occurs because `input` doesn't need to be mutated.
+    let slice = [0, 1, 2];
+    let mut input = Cow::from(&slice[..]);
+    match abs_all(&mut input) {
+        Cow::Borrowed(_) => println!("I borrowed the slice!"),
+        _ => panic!("expected borrowed value"),
     }
 
-    #[test]
-    fn reference_no_mutation() -> Result<(), &'static str> {
-        // No clone occurs because `input` doesn't need to be mutated.
-        let slice = [0, 1, 2];
-        let mut input = Cow::from(&slice[..]);
-        match abs_all(&mut input) {
-            // TODO
-        }
+    // Clone occurs because `input` needs to be mutated.
+    let slice = [-1, 0, 1];
+    let mut input = Cow::from(&slice[..]);
+    match abs_all(&mut input) {
+        Cow::Owned(_) => println!("I modified the slice and now own it!"),
+        _ => panic!("expected owned value"),
     }
 
-    #[test]
-    fn owned_no_mutation() -> Result<(), &'static str> {
-        // We can also pass `slice` without `&` so Cow owns it directly.
-        // In this case no mutation occurs and thus also no clone,
-        // but the result is still owned because it always was.
-        let slice = vec![0, 1, 2];
-        let mut input = Cow::from(slice);
-        match abs_all(&mut input) {
-            // TODO
-        }
-    }
-
-    #[test]
-    fn owned_mutation() -> Result<(), &'static str> {
-        // Of course this is also the case if a mutation does occur.
-        // In this case the call to `to_mut()` returns a reference to
-        // the same data as before.
-        let slice = vec![-1, 0, 1];
-        let mut input = Cow::from(slice);
-        match abs_all(&mut input) {
-            // TODO
-        }
+    // No clone occurs because `input` is already owned.
+    let slice = vec![-1, 0, 1];
+    let mut input = Cow::from(slice);
+    match abs_all(&mut input) {
+        // TODO
+        Cow::Borrowed(_) => println!("I own this slice!"),
+        _ => panic!("expected borrowed value"),
     }
 }
diff --git a/exercises/variables/variables1.rs b/exercises/variables/variables1.rs
index f4d182a..84de9fd 100644
--- a/exercises/variables/variables1.rs
+++ b/exercises/variables/variables1.rs
@@ -2,9 +2,7 @@
 // Make me compile!
 // Execute `rustlings hint variables1` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
-    x = 5;
+    let x = 5;
     println!("x has the value {}", x);
 }
diff --git a/exercises/variables/variables2.rs b/exercises/variables/variables2.rs
index 641aeb8..6715cf5 100644
--- a/exercises/variables/variables2.rs
+++ b/exercises/variables/variables2.rs
@@ -1,10 +1,8 @@
 // variables2.rs
 // Execute `rustlings hint variables2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
-    let x;
+    let x = 12;
     if x == 10 {
         println!("x is ten!");
     } else {
diff --git a/exercises/variables/variables3.rs b/exercises/variables/variables3.rs
index 819b1bc..30afbf1 100644
--- a/exercises/variables/variables3.rs
+++ b/exercises/variables/variables3.rs
@@ -1,9 +1,7 @@
 // variables3.rs
 // Execute `rustlings hint variables3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
-    let x: i32;
+    let x: i32 = 12;
     println!("Number {}", x);
 }
diff --git a/exercises/variables/variables4.rs b/exercises/variables/variables4.rs
index 54491b0..8c2ddd6 100644
--- a/exercises/variables/variables4.rs
+++ b/exercises/variables/variables4.rs
@@ -1,10 +1,8 @@
 // variables4.rs
 // Execute `rustlings hint variables4` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
-    let x = 3;
+    let mut x = 3;
     println!("Number {}", x);
     x = 5; // don't change this line
     println!("Number {}", x);
diff --git a/exercises/variables/variables5.rs b/exercises/variables/variables5.rs
index 0e670d2..1b9d9f4 100644
--- a/exercises/variables/variables5.rs
+++ b/exercises/variables/variables5.rs
@@ -1,11 +1,9 @@
 // variables5.rs
 // Execute `rustlings hint variables5` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
     let number = "T-H-R-E-E"; // don't change this line
     println!("Spell a Number : {}", number);
-    number = 3; // don't rename this variable
+    let number = 3; // don't rename this variable
     println!("Number plus two is : {}", number + 2);
 }
diff --git a/exercises/variables/variables6.rs b/exercises/variables/variables6.rs
index a852012..e8314b2 100644
--- a/exercises/variables/variables6.rs
+++ b/exercises/variables/variables6.rs
@@ -1,9 +1,7 @@
 // variables6.rs
 // Execute `rustlings hint variables6` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
-const NUMBER = 3;
+const NUMBER: i32 = 3;
 fn main() {
     println!("Number {}", NUMBER);
 }
diff --git a/exercises/vecs/README.md b/exercises/vecs/README.md
index 8ff9b85..ebe90bf 100644
--- a/exercises/vecs/README.md
+++ b/exercises/vecs/README.md
@@ -13,5 +13,3 @@ the other useful data structure, hash maps, later.
 ## Further information
 
 - [Storing Lists of Values with Vectors](https://doc.rust-lang.org/stable/book/ch08-01-vectors.html)
-- [`iter_mut`](https://doc.rust-lang.org/std/primitive.slice.html#method.iter_mut)
-- [`map`](https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.map)