Don L. answered • 03/31/19

Fifteen years teaching and tutoring basic math skills and algebra

Hi Theodore, the proportion to solve is:

7 / 3 = x / 9

Where x is the amount of yellow paint needed:

Cross multiply gives:

7 * 9 = 3 * x

Divide both sides by 3:

63 / 3 = x

x = 21

You would need 21 parts of yellow paint to mix with the 9 parts of blue paint.

Questions?