12 * 4 = (10 + 2) * 4 = 40 + 8 = 48
48 : 3 = (30 + 18) : 3 = 10 + 6 = 16
16 * 5 = (10 + 6) * 5 = 50 + 30 = 80
80 − 75 = 5 = a
24 : 6 = 4
4 * 4 = 16
16 + 40 = 56
56 : 14 = 4 = b
60 : 12 = 5
5 * 18 = 5 * (10 + 8) = 50 + 40 = 90
90 − 35 = 55
55 + 27 = 82 = c
3 * 30 = 90
90 − 67 = 23
23 * 2 = (20 + 3) * 2 = 40 + 6 = 46
46 − 27 = 19 = d