Correction :

19 - 11 = 8	16 + 6 = 22
40 : 5 = 8	24 + 14 = 38
15 + 15 = 30	24 + 15 = 39
18 - 5 = 13	4 + 2 = 6
1 + 16 = 17	7 × 7 = 49
17 + 4 = 21	8 : 1 = 8
10 × 8 = 80	8 : 2 = 4
13 + 10 = 23	33 : 3 = 11
16 + 15 = 31	2 + 6 = 8
4 + 15 = 19	8 × 3 = 24