Correction :

22 + 9 = 31	22 - 22 = 0
21 - 15 = 6	30 : 3 = 10
1 + 20 = 21	15 + 18 = 33
10 - 6 = 4	15 + 0 = 15
17 + 3 = 20	24 - 24 = 0
23 - 6 = 17	12 - 10 = 2
8 - 4 = 4	38 - 24 = 14
7 + 14 = 21	24 - 8 = 16
25 - 3 = 22	0 + 16 = 16
1 + 22 = 23	27 - 10 = 17