Wikijunior:Introduction to Mathematics/Subtracting
Subtracting is a way of taking a number out from an other number. It is the opposite of adding. You use the " - " sign for the subtracting operation. If you have 5 apples and give 3 to a friend, you then have 2 apples. This is 5 - 3 = 2 using the signs of mathematics.
Order is important when subtracting. 3 - 2 is not the same as 2 - 3.
Example Questions 
3+4=7, 5+10=15, 3+8=11, 2+6=8