Answer
$= \log \frac{3x^{3}y^{4}}{7}$
Work Step by Step
$= \log 3 + 3 \log x + 4 \log y - \log 7$
$= \log 3 + \log x^{3} + \log y^{4} - \log 7$
$= \log 3x^{3} + \log y^{4} - \log 7$
$= \log 3x^{3}y^{4}- \log 7$
$= \log \frac{3x^{3}y^{4}}{7}$