5. (7 points) Four girls are singing songs, accompanying each other. Each time, one of them plays the piano while the other three sing. In the evening, they counted that Anya sang 8 songs, Tanya - 6 songs, Olya - 3 songs, and Katya - 7 songs. How many times did Tanya accompany? Justify your answer.
Answer. Twice.

Solution. If we add up the specified number of songs sung, each song will be counted 3 times (from the perspective of each of the three singing girls). Thus, we can find out how many songs were sung in total: $(8+6+3+7): 3=8$. It is known that Tanya sang 6 out of 8 songs, so she accompanied $8-6=2$ times.

## Grading Criteria.

- Any correct solution - 7 points.
- The total number of songs sung is correctly found, but the answer to the problem is not obtained or is incorrect - 3 points.
- The correct answer is obtained by incomplete enumeration - 1 point.
- Only the answer is provided - 0 points.

Maximum score for all completed tasks - 35.