\[\boxed{\mathbf{799}\mathbf{.}}\]
\[1)\log_{5}3 = \frac{\log_{7}3}{\log_{7}5}\]
\[2)\lg 6 = \log_{10}6 = \frac{\log_{7}6}{\log_{7}10}\]
\[3)\log_{2}7 = \frac{\log_{7}7}{\log_{7}2} = \frac{1}{\log_{7}2}\]
\[4)\log_{5}\frac{1}{3} = \frac{\log_{7}\frac{1}{3}}{\log_{7}5}\]
\[5)\lg 7 = \log_{10}7 =\]
\[= \frac{\log_{7}7}{\log_{7}10} = \frac{1}{\log_{7}10}\]
\[6)\log_{3}7 = \frac{\log_{7}7}{\log_{7}3} = \frac{1}{\log_{7}3}\]