Условие:

Вычисли удобным способом.
56 + 9 + 4 + 11;
22 + 7 + 8 + 13;
46 + 15 + 4 + 5;
31 + 16 + 9 + 4.

56 + 9 + 4 + 11 = (56 + 4) + (9 + 11) = 60 + 20 = 80;
22 + 7 + 8 + 13 = (22 + 8) + (7 + 13) = 30 + 20 = 50;
46 + 15 + 4 + 5 = (46 + 4) + (15 + 5) = 50 + 20 = 70;
31 + 16 + 9 + 4 = (31 + 9) + (16 + 4) = 40 + 20 = 60.