Correction :

4 × 9 = 36	9 × 5 = 45
10 × 2 = 20	31 - 16 = 15
6 + 24 = 30	17 + 10 = 27
33 - 14 = 19	2 + 23 = 25
24 - 11 = 13	17 + 14 = 31
33 - 12 = 21	81 : 9 = 9
11 - 0 = 11	8 : 1 = 8
12 : 6 = 2	6 - 6 = 0
20 + 9 = 29	39 - 20 = 19
15 : 3 = 5	1 + 3 = 4