Official solution
\[y = {5^{\log x}}\]
\[ \Rightarrow \log y = \log x.log5\]
\[ \Rightarrow \log x = {{\log y} \over {\log 5}} = {\log _5}y\]
\[ \Rightarrow x = {e^{{{\log }_5}y}}\]
\[ \Rightarrow x = {y^{{{\log }_5}e}}\]
\[ \Rightarrow x = {y^{{1 \over {\log 5}}}}\]