Problem 2. In the class, two students sit at each desk. The number of desks where two boys sit is twice the number of desks where two girls sit. And the number of desks where two girls sit is twice the number of desks where a boy and a girl sit. How many boys are there in the class if there are 10 girls?

Answer: there are 18 boys in the class.
Solution. Let the number of desks where a boy and a girl sit be $x$. Then the number of desks with two girls is $2x$. Therefore, the total number of girls is $2 \cdot 2x + x = 5x = 10$, from which $x = 2$. Then the number of desks with two boys is $4x = 8$. Therefore, the total number of boys is $2 \cdot 8 + 2 = 18$.

Criteria

4 6. A complete and justified solution is provided.

In the absence of a correct solution, the highest applicable criterion from those listed below is used:

3 6. The number of desks with two girls is correctly found, but further reasoning is missing or incorrect.
3 6. The number of desks with a boy and a girl is correctly found, but further reasoning is missing or incorrect.

2 b. The correct answer is provided, but there is no justification.

06 . The problem is not solved or is solved incorrectly.