Correction :

24 : 6 = 4	17 - 12 = 5
29 - 18 = 11	36 - 15 = 21
32 - 8 = 24	1 - 1 = 0
22 + 9 = 31	22 + 21 = 43
9 + 11 = 20	27 - 6 = 21
19 + 13 = 32	27 - 3 = 24
2 : 1 = 2	44 : 4 = 11
24 + 23 = 47	21 - 18 = 3
16 + 9 = 25	15 + 5 = 20
25 - 11 = 14	63 : 7 = 9