Problem 1. When asked how old Stojan is, he replied: "If you subtract 5 from my age, divide the resulting number by 5, and then subtract 5 from that result, you will get 5." How old is Stojan?
Solution. First method. We will start solving in the reverse direction. To the number 5, which is obtained as the result, we add 5, then multiply by 5, and add 5 again to get Stojan's age. Specifically, Stojan is $(5+5) \cdot 5+5=55$ years old.

Second method. Let $x$ be the number of years Stojan has. Then from the condition of the problem we have

$$
\begin{aligned}
& (x-5): 5-5=5 \\
& (x-5): 5=10 \\
& x-5=50
\end{aligned}
$$

So Stojan is 55 years old.