Subtraction is taking away a number from another number. Addition and subtraction are important skills: you've got to be able to check that you've been given the right change, haven't you?
This 11-plus Maths quiz will give you a bit of practice in adding and subtracting.
TIP: With numbers less than 100, add the tens first and then add the units. For example:
Try to do this stuff in your head - that way next time you are out shopping, you'll know immediately if you've been short-changed or not!