Correction :

38 - 21 = 17	21 - 10 = 11
6 : 3 = 2	21 - 21 = 0
13 + 12 = 25	13 + 20 = 33
16 : 2 = 8	44 - 24 = 20
36 - 19 = 17	12 + 17 = 29
24 - 22 = 2	4 + 8 = 12
24 + 16 = 40	20 - 14 = 6
33 - 14 = 19	4 - 1 = 3
41 - 22 = 19	3 + 12 = 15
4 × 10 = 40	17 + 7 = 24