Answer
(a) $\frac{\log x}{\log 2.6}$
(b) $\frac{\ln x}{\ln 2.6}$
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) $\log_{2.6}x=\frac{\log x}{\log 2.6}$
(b) $\log_{2.6}x=\frac{\ln x}{\ln 2.6}$
