Correction :

21 - 11 = 10	7 : 7 = 1
18 + 9 = 27	16 - 13 = 3
12 + 24 = 36	11 + 9 = 20
17 - 9 = 8	16 - 8 = 8
9 - 7 = 2	6 × 11 = 66
20 + 24 = 44	0 + 1 = 1
2 + 7 = 9	8 + 6 = 14
23 + 5 = 28	110 : 10 = 11
17 - 7 = 10	4 × 4 = 16
0 + 11 = 11	13 - 10 = 3