Answer :

konrad509
[tex]15x+3x=90\\ 18x=90\\ x=5\\\\ 15x=15\cdot5=\boxed{75}[/tex]
Jerboa
90/3 = 30
30*15=450 Students

To check: 15:3  (divide by three)
                   5:1
So should be five times as many students.
90*5=450 :) Hope this helps :)

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