55 Реши уравнение: 1) \(\frac{450}{x}\) = 9; 2) \(\frac{y}{7}\) = 9; 3) \(\frac{9 + a}{9}\) = 23; 4) \(\frac{504}{b - 18}\) = 72.

• 1) $$\frac{450}{x} = 9$$ $$x = \frac{450}{9}$$ $$x = 50$$
• 2) $$\frac{y}{7} = 9$$ $$y = 9 \cdot 7$$ $$y = 63$$
• 3) $$\frac{9 + a}{9} = 23$$ $$9 + a = 23 \cdot 9$$ $$9 + a = 207$$ $$a = 207 - 9$$ $$a = 198$$
• 4) $$\frac{504}{b - 18} = 72$$ $$504 = 72 \cdot (b - 18)$$ $$b - 18 = \frac{504}{72}$$ $$b - 18 = 7$$ $$b = 7 + 18$$ $$b = 25$$

Ответ: 1) 50; 2) 63; 3) 198; 4) 25.