Correction :

12 - 9 = 3	30 - 12 = 18
31 - 14 = 17	18 - 10 = 8
2 + 4 = 6	2 × 8 = 16
8 - 8 = 0	12 - 3 = 9
5 × 10 = 50	7 × 9 = 63
13 + 24 = 37	17 + 8 = 25
0 + 20 = 20	9 × 4 = 36
24 - 12 = 12	55 : 11 = 5
2 + 9 = 11	36 - 20 = 16
21 + 22 = 43	32 - 19 = 13