Correction :

8 : 1 = 8	35 - 15 = 20
16 + 1 = 17	37 - 13 = 24
23 - 5 = 18	21 + 14 = 35
31 - 7 = 24	4 + 1 = 5
12 - 9 = 3	23 - 3 = 20
40 : 10 = 4	12 - 2 = 10
3 × 1 = 3	4 + 15 = 19
18 - 17 = 1	40 - 21 = 19
11 - 4 = 7	11 : 11 = 1
8 - 0 = 8	15 - 9 = 6