Added result of maths expressions

Added comments to show result of console log of the maths expressions, consistent with the comment showing the result of the console log of the strings values.

Author: TomHodson91

js/lesson2/tutorial.md

@@ -64,19 +64,19 @@ var x = 6;
 var y = 3;
 var addition = x + y;
 
-console.log('Addition: x + y = ' + addition);
+console.log('Addition: x + y = ' + addition); // Addition: x + y = 9
 
 var subtraction = x - y;
 
-console.log('Subtraction: x - y = ' + subtraction);
+console.log('Subtraction: x - y = ' + subtraction); // Subtraction: x - y = 3
 
 var multiplication = x * y;
 
-console.log('Multiplication: x * y = ' + multiplication);
+console.log('Multiplication: x * y = ' + multiplication); // Multiplication: x * y = 18
 
 var division = x / y;
 
-console.log('Division: x / y = ' + division);
+console.log('Division: x / y = ' + division); // Division: x / y = 2
 ```
 
 > Why not try some other maths problem using the `x` and `y` variables?