ALGEBRA
posted by JAY10 on .
A painter is to mix green and yellow paint in the ratio of 4 to 7 to obtain the color she wants. If she has 28 liters of green paint, how many liters of yellow paint should be added?
I need to know what algebraic equation I need to use...I believe this is a proportion type question....

let the amount of yellow paint be y L
then 28/y = 4/7
4y = 196
y = 49
notice 28:49 = 4:7