Correction :

18 + 15 = 33	23 - 9 = 14
3 + 13 = 16	26 - 11 = 15
17 + 3 = 20	22 - 14 = 8
39 - 21 = 18	5 × 7 = 35
2 + 16 = 18	7 + 4 = 11
32 : 8 = 4	5 + 19 = 24
28 - 7 = 21	3 + 17 = 20
18 - 16 = 2	90 : 10 = 9
19 - 11 = 8	6 - 5 = 1
30 - 11 = 19	11 + 14 = 25