Answer
$7,000 \text{ gal}$
Work Step by Step
Convert by multiplying $\dfrac{200 \text{ gal}}{1 \text{ yd}^3}$ to obtain:
$=\require{cancel}
35 \cancel{\text{ yd}^3} \cdot \dfrac{200\text{ gal}}{1 \cancel{\text{ yd}^3}}
\\=35(200) \text{ gal}
\\=7,000 \text{ gal}$