## Intermediate Algebra (6th Edition)

The quotient property of logarithms tells us that $log_{b}\frac{x}{y}=log_{b}x-log_{b}y$ (where x, y, and, b are positive real numbers and $b\ne1$). Therefore, $log_{9}\frac{21}{3}=log_{9}21-log_{9}3$. Also, $log_{9}\frac{21}{3}=log_{9}7$, because $\frac{21}{3}$ reduces to 7. So, answer choices a and d are correct.