Correction :

21 + 8 = 29	1 × 2 = 2
13 - 2 = 11	16 - 6 = 10
1 × 9 = 9	2 + 18 = 20
19 + 6 = 25	12 + 23 = 35
19 + 12 = 31	19 + 10 = 29
34 - 19 = 15	21 - 10 = 11
18 - 9 = 9	16 + 4 = 20
15 : 5 = 3	13 + 4 = 17
17 - 2 = 15	12 + 13 = 25
6 + 7 = 13	2 - 2 = 0