Correction :

7 + 20 = 27	24 - 12 = 12
31 - 23 = 8	7 × 11 = 77
18 + 1 = 19	4 + 3 = 7
2 + 6 = 8	5 - 0 = 5
6 × 2 = 12	12 - 2 = 10
7 + 21 = 28	30 : 10 = 3
20 + 15 = 35	13 + 14 = 27
14 + 18 = 32	0 + 15 = 15
19 - 2 = 17	22 - 20 = 2
37 - 17 = 20	23 + 9 = 32