Условие:

28 − 3
76 − 4
59 − 40
86 − 60

28 − 3 = (20 + 8) − 3 = 20 + (8 − 3) = 20 + 5 = 25
76 − 4 = (70 + 6) − 4 = 70 + (6 − 4) = 70 + 2 = 72
59 − 40 = (50 + 9) − 40 = 9 + (50 − 40) = 9 + 10 = 19
86 − 60 = (80 + 6) − 60 = 6 + (80 − 60) = 6 + 20 = 26