Correction :

12 + 8 = 20	0 + 9 = 9
20 + 4 = 24	24 + 5 = 29
8 + 21 = 29	23 - 8 = 15
14 + 12 = 26	19 + 2 = 21
15 + 10 = 25	7 + 21 = 28
10 - 8 = 2	30 : 6 = 5
21 - 8 = 13	19 + 24 = 43
31 - 10 = 21	16 - 0 = 16
36 - 19 = 17	13 + 3 = 16
0 + 7 = 7	34 - 15 = 19