The first group and the second group know that the position of the exchange addend and the sum are unchanged.

Adding and subtracting one addend equals another addend.

From the third and fourth groups, we can know that the subtraction of the minuend is equal to the difference, and the subtraction of the minuend is equal to the subtraction.

Difference addition and subtraction equals minuend.

Addition is the inverse of subtraction, and subtraction is the inverse of addition.