Answer: 9 gallons
Step-by-step explanation:
Given: Ratio of colors in painting:
4 parts blue, 3 parts red, and 3 parts green.
Total parts = 4+3+3 =10
Fraction of blue = [tex]\dfrac{\text{Number of parts of blue}}{\text{total parts}}=\dfrac{4}{10}[/tex]
Since, Quantity of blue color used = 12 gallons
Let total quantity of color be x,
[tex]\dfrac{4}{10}x=12\\\\\Rightarrow\ x=\dfrac{120}{4}=30\text{ gallons}[/tex]
Total color used = 30 gallons
Color used for green part only = [tex]\dfrac{3}{10}\times30 = \text{9 gallons}[/tex]
Hence, 9 gallons of paint were needed for the green part of the painting.