1) 48 + x = 56
x = 56 - 48
x = 8
Проверка:
48 + 8 = 56;
2) 66 - x = 24
x = 66 - 24
x = 42
66 - 42 = 24;
3) y - 26 = 72
y = 72 + 26
y = 98
98 - 26 = 72.