Correction :

21 + 8 = 29	28 - 9 = 19
4 + 7 = 11	44 : 4 = 11
16 + 12 = 28	9 × 3 = 27
28 : 7 = 4	6 + 21 = 27
14 - 11 = 3	21 + 13 = 34
15 - 7 = 8	10 + 17 = 27
6 × 3 = 18	46 - 23 = 23
20 - 16 = 4	3 + 6 = 9
26 - 17 = 9	22 - 19 = 3
12 + 8 = 20	110 : 11 = 10