Subtraction is used to calculate how much is more and how much is less. 15 minus 7 equals 8, and 15 equals 8. When solving this problem, we know that we should first make clear the meaning of the topic, and then write. It is known that 15 is 7 more than me, and the number of 7 more than me is 8.

This topic is an example of subtraction in grade one. Its teaching purpose is to let us know that subtraction by minuend equals difference, subtraction by minuend equals difference, and addition and subtraction by minuend equals difference. These are three basic formulas and a basic knowledge point in subtraction. According to the known conditions, 15 is 7 more than me, and 15 subtracts 7 as much as me, so this explanation is the usual method.