Answer
(a) $\frac{\log\frac{3}{10}}{\log x}$
(b) $\frac{\ln\frac{3}{10}}{\ln x}$
Work Step by Step
Just apply the Change-of-Base Formula: $\log_ax=\frac{\log x}{\log a}~or~\log_ax=\frac{\ln x}{\ln a}$.
(a) $\log_{x}\frac{3}{10}=\frac{\log\frac{3}{10}}{\log x}$
(b) $\log_{x}\frac{3}{10}=\frac{\ln\frac{3}{10}}{\ln x}$
