Answer:
95
Step-by-step explanation:
Let 2x be how many red/green marbles there are,
let 5x be how many blue marbles there are, and
let 7x be how many white marbles there are.
2x + 2x + 5x + 7x = 304
16x = 304
x = 19
As 5x is defined as how many blue marbles there are, we could just plug x for 19:
5*19 = 95
I hope this helped, and if it did please consider giving me brainliest :)