How to solve this Mystery with Mathematics

Question

I read a mystery in a book but I can't solve it with Mathematics. The mystery is:
"I have tripled my nephew's age, and 5 years ago I have 5 times from his twin brother age. What is my age now?"
In mathematics the problem is like this:
$x=$my age , $y=$my nephew's age
$x=3y$
$x-5=5y$
but the answer from that equation is not true.
the correct answers are : $x=30$ and $y=10$. How did they solve this problem?
(sorry for my bad english)

Answer 1

Hints: using your notation, and assuming the riddle is what I wrote in the comment above, the equations are

$$\begin{align*}x&=3y\\(x-5)&=5(y-5)\end{align*}$$

Substitute the first eq. into the second one and get $\;y=10\;$ ...