Answer:
A
Explanation:
So if 45 students represent 1/5 of the school, and x is the number of students in the school, then 45 will simply represent 1/5 of x.
This means that the equation is 1/5x = 45.
Now, you have to solve the equation.

Multiply both sides of the equation by 5

This means that there are 225 students.