The organizers of the exhibition "To the Moon and Beyond" felt that they had low attendance on the first day, so they reduced the admission fee by 12 Kč. As a result, the number of visitors increased by $10\%$ on the second day, but the total daily revenue decreased by $5\%$. How many korunas did the admission cost after the discount?

(M. Petrová)
We will organize the information from the assignment into the following table:

|  | first day | second day |
| :---: | :---: | :---: |
| number of visitors | $n$ | $1.1 n$ |
| admission fee (Kč per person) | $x+12$ | $x$ |
| total daily revenue (Kč) | $n(x+12)$ | $1.1 n x$, or $0.95 n(x+12)$ |

From the last cell of the table, we will set up an equation, which we will solve (assuming $n>0$):

$$
\begin{aligned}
1.1 n x & =0.95 n(x+12) \\
1.1 x & =0.95 x+11.4 \\
0.15 x & =11.4 \\
x & =76
\end{aligned}
$$

The admission fee after the discount was 76 Kč.

Evaluation. 3 points for setting up the table or its equivalent, of which 1 point for the information in the first two rows under the header and 2 points for the information in the last row; 2 points for setting up and solving the equation; 1 point for the result.

If the solver includes in their work a variant that no one arrived on the first day, i.e., $n=0$, and that the admission fee after the discount could therefore be anything, this cannot be accepted as a solution to the problem. (The assignment states that the number of visitors increased by 10% on the second day.) However, if the solver adds this variant to the correct solution of the problem, do not deduct points for it.