Correction :

17 + 18 = 35	21 + 3 = 24
1 + 0 = 1	30 - 22 = 8
18 - 18 = 0	4 - 2 = 2
15 - 13 = 2	15 - 9 = 6
36 - 13 = 23	43 - 23 = 20
4 - 4 = 0	35 - 17 = 18
26 - 12 = 14	5 : 1 = 5
4 + 12 = 16	26 - 10 = 16
20 + 8 = 28	42 : 7 = 6
23 - 10 = 13	0 + 18 = 18