3. The numbers from 1 to 25 (each exactly once) were placed in the cells of a $5 \times 5$ square such that the sum of the numbers in each row and each column is the same. A boy erased all the numbers except for four (see the picture). Find the number marked with a circle $\bigcirc$.

![](https://cdn.mathpix.com/cropped/2024_05_06_2c88e986557291f915d2g-1.jpg?height=322&width=323&top_left_y=1695&top_left_x=912)
Solution. The sum of all numbers $1+2+3+\ldots+25=325$, so the sum of the numbers in one row is $325: 5=65$. Now let's find the unknown number $65-(10+18+1+22)=$ $65-51=14$. Answer: 14.