Correction :

15 + 24 = 39	22 + 17 = 39
7 × 9 = 63	20 - 8 = 12
3 + 13 = 16	15 + 21 = 36
21 - 8 = 13	6 : 3 = 2
12 - 7 = 5	4 + 3 = 7
20 : 2 = 10	0 + 16 = 16
30 : 3 = 10	24 + 19 = 43
6 : 3 = 2	31 - 8 = 23
6 + 8 = 14	17 - 5 = 12
4 + 16 = 20	13 - 11 = 2