Answer: 9 gallons
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 =
![\frac{\text{Number of parts of blue}}{\text{total parts}}=(4)/(10)](https://img.qammunity.org/2021/formulas/mathematics/high-school/o9qxbu9xdihfbfkgzeeoscg9b1xfx3v7xr.png)
Since, Quantity of blue color used = 12 gallons
Let total quantity of color be x,
![(4)/(10)x=12\\\\\Rightarrow\ x=(120)/(4)=30\text{ gallons}](https://img.qammunity.org/2021/formulas/mathematics/high-school/furhosna1xwyel53d0ptegygaormf2ze1w.png)
Total color used = 30 gallons
Color used for green part only =
![(3)/(10)*30 = \text{9 gallons}](https://img.qammunity.org/2021/formulas/mathematics/high-school/is3fylaidw8nhfio5e4c07f9h79hr1oi9d.png)
Hence, 9 gallons of paint were needed for the green part of the painting.