Correction :

21 + 16 = 37	8 - 8 = 0
22 - 1 = 21	19 + 16 = 35
12 - 5 = 7	7 + 4 = 11
32 - 13 = 19	1 + 14 = 15
35 - 23 = 12	25 - 20 = 5
31 - 21 = 10	21 + 15 = 36
24 - 2 = 22	43 - 21 = 22
14 + 5 = 19	8 × 10 = 80
29 - 8 = 21	15 + 1 = 16
20 - 20 = 0	4 × 8 = 32