Correction :

22 - 20 = 2	42 - 24 = 18
0 + 7 = 7	23 - 7 = 16
20 + 12 = 32	12 : 6 = 2
9 + 3 = 12	13 + 0 = 13
20 : 4 = 5	9 + 20 = 29
3 + 24 = 27	20 - 19 = 1
35 : 5 = 7	22 + 0 = 22
14 + 21 = 35	24 + 20 = 44
40 - 17 = 23	23 + 0 = 23
14 - 14 = 0	21 - 2 = 19