#### Answer

For $x = \frac{1}{2}$ the answer is $y = \frac{1}{10}$,
for $ y = -5$ the answer is $x = -25$.

#### Work Step by Step

We receive the first result by inserting $x = \frac{1}{2}$ in $x = 5y$:
$ \frac{1}{2} = 5 y \Rightarrow \frac{1 }{2 \cdot 5} = y \Rightarrow \frac{1}{10} = y$.
We receive the second result by inserting $y = -5$ in $x = 5y$:
$ x = 5 \cdot (-5) \Rightarrow x = - 5 \cdot 5 \Rightarrow x = -25$.