So if 3/4 of the seats are filled, there are a few methods we can use.
The simplest method:
Just multiply 3/4 by 500, to get 1500/4, or 375.
So 375 seats are filled.
A method that can be used with harder problems and will be more efficient in those cases:
Using proportions.
You could say,
?/500 = 3/4
And then cross multiply,
500 * 3 = 4 * x (say the ? = x)
1500 = 4x
/4 /4
x = 375
So either way we get the answer, 375 seats were filled.