Correction :

21 + 16 = 37	20 - 17 = 3
14 + 7 = 21	15 + 8 = 23
7 + 18 = 25	9 - 9 = 0
72 : 8 = 9	9 - 1 = 8
8 + 21 = 29	26 - 10 = 16
23 + 11 = 34	63 : 9 = 7
40 - 19 = 21	0 + 11 = 11
13 + 24 = 37	24 - 14 = 10
3 + 22 = 25	40 - 24 = 16
11 + 6 = 17	23 - 13 = 10