Astudents cost for last semester at her community college was $2500. she spent $475 of that on books. what percent of last semesters college cost was spent on books?

It is 19%!! :) an explanation is:
We assume, that the number 2500 is 100% - because it's the output value of the task.
2. We assume, that x is the value we are looking for.
3. If 100% equals 2500, so we can write it down as 100%=2500.
4. We know, that x% equals 475 of the output value, so we can write it down as x%=475.
5. Now we have two simple equations:
1) 100%=2500
2) x%=475
where left sides of both of them have the same units, and both right sides have the same units, so we can do something like that:
100%/x%=2500/475
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for 475 is what percent of 2500

100%/x%=2500/475
(100/x)*x=(2500/475)*x - we multiply both sides of the equation by x
100=5.2631578947368*x - we divide both sides of the equation by (5.2631578947368) to get x
100/5.2631578947368=x
19=x
x=19

now we have:
475 is 19% of 2500