Correction :

15 - 7 = 8	60 : 6 = 10
12 + 9 = 21	30 : 5 = 6
24 + 11 = 35	16 - 10 = 6
20 - 16 = 4	26 - 14 = 12
22 - 7 = 15	15 - 0 = 15
39 - 23 = 16	34 - 19 = 15
9 - 9 = 0	22 - 7 = 15
6 + 11 = 17	10 - 10 = 0
12 + 7 = 19	16 - 9 = 7
5 + 20 = 25	24 - 2 = 22