3. Last year, the number of students (girls and boys) in a certain school was 850. This year, the number of boys decreased by $4 \%$, and the number of girls increased by $3 \%$, after which the number of students in the school is 844. What is the number of girls in the school this year?
3. Let $x$ be the number of girls in the school last year.

Then $850-x$ is the number of boys last year.

$1 \text{ POINT}$

This year, the number of girls is $x+3\%x=1.03x$,

$1 \text{ POINT}$

and the number of boys is $850-x-4\%(850-x)=0.96(850-x)$.

$1 \text{ POINT}$

We have $1.03x + 0.96(850-x) = 844$

$1 \text{ POINT}$

so $x = 400$

$1 \text{ POINT}$

or $1.03x = 412$.

This year, the number of girls in the school is 412.

$1 \text{ POINT}$

TOTAL 6 POINTS