Problem 3. One notebook, 3 notepads, and 2 pens cost 98 rubles, while 3 notebooks and a notepad are 36 rubles cheaper than 5 pens. How much does each item cost, if the notebook costs an even number of rubles? (Each of these items costs a whole number of rubles.)
Answer: $4,22,14$.

Solution. Let the required costs be $-x, y$ and $z$. The condition gives the system

$$
\left\{\begin{array}{l}
x+3 y+2 z=98 \\
3 x+y-5 z=-36
\end{array}\right.
$$

Multiply the first equation by 3 and subtract the second from it. We get that $8 y+11 z=330$. It is clear that $y$ must be divisible by 11. Accordingly, $y$ can be 11, 22, or 33.

But from the first equation of the system, it is clear that, for $x$ to be even, $y$ must also be even. Therefore, $y=22, z=14, x=4$.