16 ){\begin{aligned}5^{y}\cdot 25^{x} &= 625\\(\frac{1}{3})^{x}\cdot 9^{y} &= \frac{1}{27}\end{aligned}}

$$\begin{aligned}&\begin{cases}5^{y}\cdot 25^{x} = 625\\(\frac{1}{3})^{x}\cdot 9^{y} = \frac{1}{27}\end{cases}\\&\begin{cases}5^{y}\cdot (5^{2})^{x} = 5^{4}\\(\frac{1}{3})^{x}\cdot (3^{2})^{y} = \frac{1}{27}\end{cases}\\&\begin{cases}5^{y}\cdot 5^{2x} = 5^{4}\\3^{-x}\cdot 3^{2y} = 3^{-3}\end{cases}\\&\begin{cases}y+2x = 4\\-x+2y = -3\end{cases}\end{aligned}$$ Выразим y из первого уравнения: $$\begin{aligned}&y = 4 - 2x\end{aligned}$$ Подставим значение y во второе уравнение: $$\begin{aligned}&-x+2(4-2x) = -3\\&-x+8-4x = -3\\&-5x = -11\\&x = \frac{11}{5}\end{aligned}$$ Тогда: $$\begin{aligned}&y = 4 - 2\cdot \frac{11}{5}\\&y = 4 - \frac{22}{5}\\&y = -\frac{2}{5}\end{aligned}$$ Ответ: x=11/5; y=-2/5