More var stuff

rustbook/variables/src/main.rs

@@ -1,6 +1,9 @@
 fn main() {
-    let mut x = 5;
-    println!("The value of x is: {}", x);
-    x = 6;
+    let x = 5;
+
+    let x = x + 1;
+
+    let x = x * 2;
+
     println!("The value of x is: {}", x);
 }