The concept that is useful to answering the question above is the ratio -proportion. Let x be the number of white paint that should be used in the mixture. The ratio - proportion expression of the given above is ,
5 parts / 2 parts = 8.5 quarts / x quarts
Solving for x gives an answer of x = 3.4. Thus, 3.4 quarts of white paint should be used for the mixture.