Условие:

Вычисли.
7 + 50 + 3 + 30
80 + 8 + 10 + 2

7 + 50 + 3 + 30 = (50 + 30) + (7 + 3) = 80 + 10 = 90
80 + 8 + 10 + 2 = (80 + 10) + (8 + 2) = 90 + 10 = 100