Correction :

19 - 19 = 0	2 + 5 = 7
4 + 9 = 13	21 - 3 = 18
20 - 16 = 4	22 + 1 = 23
42 - 20 = 22	22 - 2 = 20
18 + 15 = 33	15 : 5 = 3
18 : 9 = 2	1 - 0 = 1
15 + 0 = 15	46 - 23 = 23
23 + 12 = 35	11 + 17 = 28
30 : 5 = 6	43 - 24 = 19
37 - 15 = 22	19 - 4 = 15