what is a set of related addition and subtraction number sentences useing the same numbers
2 + 5 = 7
7 - 2 = 5
10 + 4 = 14
14 - 4 = 10
15 - 7 = 8
15 - 8 = 7
8 + 7 = 15
7 + 8 = 15
7 - 2 = 5
10 + 4 = 14
14 - 4 = 10
15 - 8 = 7
8 + 7 = 15
7 + 8 = 15