Addition: 20 + 67 = 87

Subtraction: 67 - 20 = 47

Multiplication: 67*20 = 1340

Division: 67/20 = 3.35

Pre-increment: ++67 = 68

Post-increment: 68++ = 68

Pre-decrement: --20 = 19

Post-decrement: 19-- = 19

Addition will result in the sum of $num1 and $num2

Subtraction will result in the difference of $num2 and $num1

Multiplication will result in the product of $num2 and $num1

Division will result in the quotient of $num2 and $num1

Modulus will result in the remainder of $num2 and $num1

Pre-increment will result in the incremention of $num2. ++ before the varaible will result in the variable being incremented first and then the value being returned.

Post-increment will result in the incremention of $num2. ++ after the varaible will result in the variable being returned first and then it is incremented. Hence why the value of $num2 stays the same.

Pre-decrement will result in the decrement of $num1. -- before the varaible will result in the variable being decremented first and then the value being returned.

Post-decrement will result in the decrement of $num1. -- after the varaible will result in the variable being returned first and then it is decremented. Hence why the value of $num1 stays the same.