Correction :

12 + 8 = 20	2 + 13 = 15
64 : 8 = 8	12 - 12 = 0
29 - 20 = 9	28 - 17 = 11
15 - 12 = 3	9 × 2 = 18
43 - 19 = 24	32 - 24 = 8
1 + 4 = 5	7 + 2 = 9
20 : 2 = 10	41 - 22 = 19
20 : 10 = 2	20 - 3 = 17
7 + 12 = 19	35 - 24 = 11
18 : 6 = 3	2 × 10 = 20