3. For every 7 boys in a school, there are 8 girls, and for every 9 boys, there is one teacher. In this school, there are a total of 675 students. How many teachers are there in this school?
First method:

In the school, there is a certain number of groups with $7+8=15$ students. 1 POINT

There are $675: 15=45$ such groups. 1 POINT

The number of boys is $45 \cdot 7=315$. 2 POINTS

Since 1 teacher is assigned to every 9 boys and $315: 9=35$,

there are 35 teachers in the school.

2 POINTS

TOTAL 6 POINTS