Correction :

47 - 23 = 24	28 - 13 = 15
15 - 14 = 1	2 × 4 = 8
21 + 19 = 40	17 + 2 = 19
10 × 8 = 80	22 + 0 = 22
18 - 12 = 6	24 - 19 = 5
18 : 9 = 2	15 + 9 = 24
8 - 5 = 3	1 × 8 = 8
40 - 23 = 17	3 × 1 = 3
22 - 22 = 0	34 - 20 = 14
5 + 7 = 12	5 + 16 = 21