Correction :

12 + 2 = 14	33 - 9 = 24
23 + 8 = 31	30 - 24 = 6
19 + 24 = 43	4 + 23 = 27
15 + 10 = 25	22 - 15 = 7
17 + 18 = 35	23 - 14 = 9
4 + 13 = 17	10 × 3 = 30
11 × 8 = 88	42 - 24 = 18
17 + 10 = 27	28 - 21 = 7
31 - 14 = 17	28 : 7 = 4
23 + 21 = 44	7 - 5 = 2