Correction :

9 : 9 = 1	24 - 10 = 14
19 - 7 = 12	1 × 4 = 4
39 - 20 = 19	11 - 7 = 4
18 - 6 = 12	21 + 7 = 28
19 - 5 = 14	13 + 3 = 16
16 - 11 = 5	23 + 14 = 37
22 - 8 = 14	21 - 21 = 0
22 - 7 = 15	10 : 5 = 2
8 - 1 = 7	81 : 9 = 9
110 : 10 = 11	49 : 7 = 7