Correction :

4 : 2 = 2	20 - 19 = 1
11 - 6 = 5	16 - 3 = 13
9 + 13 = 22	25 - 19 = 6
19 - 7 = 12	39 - 24 = 15
7 - 1 = 6	17 + 9 = 26
6 × 8 = 48	23 + 8 = 31
10 × 10 = 100	4 × 5 = 20
19 + 12 = 31	11 - 5 = 6
19 - 18 = 1	15 - 6 = 9
11 - 11 = 0	13 + 24 = 37