5.2 Six children stood in a circle and whispered their favorite number to the neighbors on their right and left. Each child added the two numbers they heard and said them out loud. The picture shows what three of the children said. What number did the girl think of, next to whom there is a question mark?

![](https://cdn.mathpix.com/cropped/2024_05_06_e33eb8c1d213348b709ag-07.jpg?height=483&width=602&top_left_y=1860&top_left_x=727)
Answer: 5.

Solution. Let's add the numbers we know: $8+14+12=34$. We get that 34 is the numbers marked on the diagram as A, B, and under the question mark, but taken twice. Therefore, 34:2 = 17, and the sum of the numbers A and B is 12. Thus, the girl guessed the number 5, which can be found by subtracting 12 from 17.

![](https://cdn.mathpix.com/cropped/2024_05_06_e33eb8c1d213348b709ag-08.jpg?height=386&width=472&top_left_y=144&top_left_x=1403)