Adam and Eve were playing chess.

Adam won and comforted Eve: "You know, I've been playing chess for a long time, twice as long as you!" Eve got upset: "But last time you said you've been playing three times longer!"

Adam was surprised: "Did I say that? And when was that?"

"Two years ago!"

"Well, then I was telling the truth - and I am today as well."

How long has Adam been playing chess?

(M. Volfová)
Let's assume that Eva has been playing chess for $x$ years. Then the time data appearing in the problem can be briefly expressed in the following table:

|  | last year | today |
| :---: | :---: | :---: |
| Eva | $x-2$ | $x$ |
| Adam | $2 x-2$ | $2 x$ |

Last year, Adam played chess three times longer than Eva, which we can express with the equation:

$$
\begin{aligned}
2 x-2 & =3(x-2), \\
2 x-2 & =3 x-6, \\
4 & =x .
\end{aligned}
$$

Thus, $2 x=8$, which means Adam has been playing chess for 8 years.

Evaluation. 2 points for data corresponding to our table; 2 points for setting up and solving the equation; 2 points for the correct conclusion.