Условие:

Вычисли и проверь решение:
75 + 12
94 − 32
56 + 24
14 − 2

75 + 12 = (70 + 5) + (10 + 2) = (70 + 10) + (5 + 2) = 80 + 7 = 87
Проверка:
1) 87 − 12 = 87 − 7 − 5 = 80 − 5 = 75;
2) 87 − 75 = 87 − 5 − 70 = 82 − 70 = 12.
 
94 − 32 = (90 + 4) − (30 + 2) = (90 − 30) + (4 − 2) = 60 + 2 = 62
Проверка:
1) 62 + 32 = (60 + 2) + (30 + 2) = (60 + 30) + (2 + 2) = 90 + 4 = 94;
2) 94 − 62 = (90 + 4) − (60 + 2) = (90 − 60) + (4 − 2) = 30 + 2 = 32.
 
56 + 24 = (50 + 6) + (20 + 4) = (50 + 20) + (6 + 4) = 70 + 10 = 80
Проверка:
1) 80 − 24 = 80 − 20 − 4 = 60 − 4 = 56;
2) 56 + 24 = (50 + 6) + (20 + 4) = (50 + 20) + (6 + 4) = 70 + 10 = 80.
 
14 − 2 = (10 + 4) − 2 = 10 + (4 − 2) = 10 + 2 = 12.
Проверка:
1) 12 + 2 = (10 + 2) + 2 = 10 + (2 + 2) = 10 + 4 = 14;
2) 14 − 12 = (10 + 4) − (10 + 2) = (10 − 10) + (4 − 2) = 0 + 2 = 2.