100 − (3 + 67)
(62 + 18) − 45
59 + 16 + 4
35 + 5 + 28
21 − 9
43 + 9
100 − (3 + 67) = 100 − 70 = 30
(62 + 18) − 45 = 80 − 45 = 80 − 40 − 5 = 40 − 5 = 35
59 + 16 + 4 = 59 + (16 + 4) = 59 + 20 = 79
35 + 5 + 28 = 40 + 28 = 68
21 − 9 = (1 + 20) − 9 = 1 + (20 − 9) = 1 + 11 = 12
43 + 9 = (40 + 3) + 9 = 40 + (3 + 9) = 40 + 12 = 52