Correction :

3 + 12 = 15	30 - 6 = 24
2 - 1 = 1	13 - 8 = 5
13 + 13 = 26	36 - 13 = 23
25 - 10 = 15	11 × 5 = 55
2 : 2 = 1	31 - 21 = 10
25 - 20 = 5	3 + 24 = 27
35 - 21 = 14	11 - 6 = 5
24 + 2 = 26	36 - 17 = 19
9 × 10 = 90	21 + 16 = 37
2 : 1 = 2	6 + 9 = 15