Answer
$9 \text{ gal}$
Work Step by Step
Convert by multiplying $\dfrac{1 \text{ gal}}{231 \text{ in.}^3}$ to obtain:
$=\require{cancel}
2079 \cancel{\text{ in.}^3} \cdot \dfrac{1\text{ gal}}{231 \cancel{\text{ in.}^3}}
\\=\dfrac{2079}{231} \text{ gal}
\\=9 \text{ gal}$