Correction :

1 + 11 = 12	27 - 14 = 13
16 + 15 = 31	9 + 1 = 10
3 + 21 = 24	12 : 3 = 4
11 - 5 = 6	26 - 16 = 10
13 - 4 = 9	5 + 2 = 7
20 - 12 = 8	22 + 18 = 40
21 + 7 = 28	19 + 13 = 32
15 + 11 = 26	7 + 10 = 17
25 - 4 = 21	16 - 13 = 3
45 : 9 = 5	12 + 11 = 23