Correction :

1 + 21 = 22	21 + 16 = 37
20 - 12 = 8	36 : 6 = 6
7 + 5 = 12	16 + 24 = 40
9 + 3 = 12	17 + 1 = 18
13 + 15 = 28	26 - 8 = 18
14 + 19 = 33	15 - 6 = 9
42 - 19 = 23	7 × 1 = 7
31 - 10 = 21	8 + 20 = 28
24 + 23 = 47	17 + 20 = 37
21 - 14 = 7	21 + 11 = 32