Correction :

7 + 5 = 12	24 + 9 = 33
10 × 8 = 80	27 - 23 = 4
34 - 15 = 19	35 - 16 = 19
31 - 16 = 15	10 - 6 = 4
6 - 3 = 3	18 + 0 = 18
31 - 22 = 9	7 × 2 = 14
24 + 10 = 34	23 - 7 = 16
42 - 20 = 22	18 - 18 = 0
72 : 9 = 8	20 + 17 = 37
24 - 19 = 5	31 - 9 = 22