The longer sides of the rectangles should be the same value, so we can make the lower part of the equation equal to 18, which is 4.
We can even find the y value by making it equal to 10, which is 3.
There are 15 girls in the classroom
I cant tell if this is french or spanish but please translate so we can try to help you
Answer in image.
Knowledge point: Trigonometry - tangent concept