\[\boxed{\mathbf{665}.}\]
\[1)\ 5^{x} = \frac{1}{5};\]
\[5^{x} = 5^{- 1};\]
\[Ответ:\ \ x = - 1.\]
\[2)\ 7^{x} = 49;\]
\[7^{x} = 7^{2};\]
\[Ответ:\ \ x = 2.\]
\[3)\ \left( \frac{1}{3} \right)^{x} = \sqrt{3};\]
\[3^{- x} = 3^{\frac{1}{2}};\]
\[- x = \frac{1}{2};\]
\[Ответ:\ \ x = - \frac{1}{2}.\]
\[4)\ \left( \frac{1}{7} \right)^{x} = \sqrt[3]{7};\]
\[7^{- x} = 7^{\frac{1}{3}};\]
\[- x = \frac{1}{3};\]
\[Ответ:\ \ x = - \frac{1}{3}.\]