Условие:

Вычисли удобным способом.
1 + 5 + 9 + 15;
18 + 7 + 13 + 22;
26 + 19 + 20 + 4;
47 + 35 + 13.

1 + 5 + 9 + 15 = (1 + 9) + (5 + 15) = 10 + 20 = 30;
18 + 7 + 13 + 22 = (18 + 22) + (7 + 13) = 40 + 20 = 60;
26 + 19 + 20 + 4 = (26 + 4) + 20 + 19 = 30 + 20 + 19 = 50 + 19 = 69;
47 + 35 + 13 = (47 + 13) + 35 = 60 + 35 = 95.