Question

A certain paint is to be mixed with 3 parts yellow to 2 parts blue. Twelve gallons of mixed paint are needed.

How many gallons of blue must be used?

Answer 1

This is a proportional reasoning question.
The proportion is blue/total paint=blue/total paint
so the question gave you
2blue/(5 total from 2blue+3yellow) and you are asked How many blue for 12 gallons.
So 2/5=BLUE/12
(12)[2/5]=12[Blue/12]
and solve : )

Answer 2

X gal. of blue.
3x/2 = 1.5x gal. of yel.

x + 1.5x = 12.

Answer 3

Yes, both ways have the same answer : )