We can set up a proportion since we know the ratio between the # of purple marbles and the # of green marbles.
A ratio is a way to compare two different values: for every 8 purple marbles there are 5 green marbles
![(8)/(5) = (p)/(30)](https://img.qammunity.org/2021/formulas/mathematics/college/hz9hjuzas8aryu2klz2b5g13d46p85d8ls.png)
when we cross multiply, we get 5p = 240
we divide both sides by 5 to isolate the variable
There are 48 purple marbles