Correction :

4 + 16 = 20	15 - 6 = 9
3 : 3 = 1	16 - 10 = 6
3 × 7 = 21	19 - 10 = 9
16 : 4 = 4	29 - 8 = 21
1 + 13 = 14	5 + 21 = 26
16 - 2 = 14	5 - 2 = 3
5 + 21 = 26	24 + 9 = 33
10 + 21 = 31	25 - 7 = 18
5 + 15 = 20	7 + 21 = 28
8 × 4 = 32	18 + 9 = 27