The Bag of Marbles Phenomena

QUESTION:

I have a bag of marbles with a total volume of 33. There are two kinds of marbles in my bag. Blue marbles that have a volume of 3 and red marbles that have a volume of 6. If I have 8 marbles in the bag, how many blue and red marbles do I have?

I have been trying to create a code that tells me how many red and blue marbles there are but I cant seem to solve this. Any Ideas?

For this specific problem there should be 5 Blue and 3 Red.