Answer :

TacoGod
30%.

Well, the simplest way to do it is to put it as a fraction.
90/300.

This is the same as 3/10, which is the same as .30, which is the same as 30% :P

Hope this helped!
[tex]\frac{90}{300}\cdot100\%=\frac{3}{10}\cdot100\%=3\cdot10\%=30\%[/tex]