Correction :

42 - 22 = 20	27 - 14 = 13
21 - 13 = 8	16 + 1 = 17
56 : 8 = 7	19 - 7 = 12
7 × 7 = 49	8 - 1 = 7
0 + 11 = 11	12 + 24 = 36
35 - 24 = 11	19 + 7 = 26
10 - 8 = 2	2 - 1 = 1
17 + 23 = 40	24 + 2 = 26
10 - 2 = 8	22 - 8 = 14
24 - 21 = 3	3 × 9 = 27