In a school there are 458 more girls than boys. If there are 692 girls how many pupils are there in that school?
There are $x$ classes in the school.

There are $y$ pupils in each class.

There are $z$ schools.

There are $n$ pupils in each school.

There are $m$ pupils in the city.

$n = xy$

$m = zn$

Now we need to know $x$, $y$, $z$ to find $n$, $m$.