\[\boxed{\mathbf{614}\mathbf{.}}\]
\[1)\ arctg\ (5x - 1) = \frac{\pi}{4}\]
\[\text{arctg\ }(5x - 1) = arctg\ 1\]
\[5x - 1 = 1\]
\[5x = 2\]
\[x = \frac{2}{5}\]
\[x = 0,4\]
\[Ответ:\ \ x = 0,4\]
\[2)\ arctg\ (3 - 5x) = - \frac{\pi}{3}\]
\[\text{arctg\ }(3 - 5x) = arctg\ \left( - \sqrt{3} \right)\]
\[\text{arctg\ }(3 - 5x) = - arctg\ \left( \sqrt{3} \right)\]
\[3 - 5x = - \sqrt{3}\]
\[5x = 3 + \sqrt{3}\]
\[x = \frac{3 + \sqrt{3}}{5}\]
\[Ответ:\ \ x = \frac{3 + \sqrt{3}}{5}.\]