Add solutions to intro and variables

exercises/00_intro/intro2.rs

@@ -1,5 +1,5 @@
-// Make the code print a greeting to the world.
+// TODO: Fix the code to print "Hello world!".
 
 fn main() {
-    printline!("Hello there!")
+    printline!("Hello world!");
 }

exercises/01_variables/variables1.rs

@@ -1,6 +1,6 @@
-// Make me compile!
-
 fn main() {
+    // TODO: Add missing keyword.
     x = 5;
-    println!("x has the value {}", x);
+
+    println!("x has the value {x}");
 }

exercises/01_variables/variables2.rs

@@ -1,5 +1,7 @@
 fn main() {
+    // TODO: Change the line below to fix the compiler error.
     let x;
+
     if x == 10 {
         println!("x is ten!");
     } else {

exercises/01_variables/variables3.rs

@@ -1,4 +1,6 @@
 fn main() {
+    // TODO: Change the line below to fix the compiler error.
     let x: i32;
-    println!("Number {}", x);
+
+    println!("Number {x}");
 }

exercises/01_variables/variables4.rs

@@ -1,6 +1,9 @@
+// TODO: Fix the compiler error.
+
 fn main() {
     let x = 3;
-    println!("Number {}", x);
-    x = 5; // don't change this line
-    println!("Number {}", x);
+    println!("Number {x}");
+
+    x = 5; // Don't change this line
+    println!("Number {x}");
 }

exercises/01_variables/variables5.rs

@@ -1,6 +1,8 @@
 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
-    println!("Number plus two is : {}", number + 2);
+    let number = "T-H-R-E-E"; // Don't change this line
+    println!("Spell a number: {}", number);
+
+    // TODO: Fix the compiler error by changing the line below without renaming the the variable.
+    number = 3;
+    println!("Number plus two is: {}", number + 2);
 }

exercises/01_variables/variables6.rs

@@ -1,4 +1,6 @@
+// TODO: Change the line below to fix the compiler error.
 const NUMBER = 3;
+
 fn main() {
-    println!("Number {}", NUMBER);
+    println!("Number: {NUMBER}");
 }