## Task A-1.2.

In a math exam, 40 problems are solved. A correct answer is worth 15 points, while an incorrect one is worth -4 points. Dinko solved all the problems, but unfortunately, some were wrong. How many incorrect answers did he give if he had a total of 353 points?
## Solution.

Let Dinko have solved $x$ problems incorrectly. 1 point

The number of problems he solved correctly is $40-x$, 1 point

so he has a total of $15 \cdot(40-x)-4 \cdot x$ points.

Therefore, the equation to solve is

$$
15 \cdot(40-x)-4 \cdot x=353
$$

By simplifying, we get the equation $600-19 x=353$, or $19 x=247$, so the solution is $x=13$.

Dinko solved 13 problems incorrectly.

Note: The student should write what the unknown they introduced represents or write the answer at the end. If they do neither, 1 point should be deducted.