Answer
Find out the how many cups of red and blue paint would you need .
To prove
As given
Cee-Lo Green decided to paint his entire house purple .
The purple paint mixture contains
cup of blue paint and
cup of red paint.
Thus the ratio of the blue paint to the red paint is given by.

Thus

As given
same ratio to make 20 cups of purple paint .
Let us assume that the x be the scalar multiple of the blue and the red paint.
Blue paint cups = 3x
Red paint cups = 2x
2x + 3x = 20
5x = 20

x = 4
Thus
Blue paint cups = 3 × 4
= 12 cups
Red paint cups = 2 × 4
= 8 cups
Therefore 8 cups of red and 12 cupsblue paint would you need to form 20 cups of the purple paint.