Correction :

21 - 15 = 6	15 + 18 = 33
24 - 8 = 16	0 + 12 = 12
0 + 8 = 8	14 + 14 = 28
32 : 4 = 8	22 - 6 = 16
37 - 17 = 20	25 - 12 = 13
32 - 18 = 14	18 - 11 = 7
37 - 16 = 21	18 + 15 = 33
9 + 10 = 19	3 × 4 = 12
15 + 1 = 16	23 - 0 = 23
22 - 11 = 11	21 - 19 = 2