Реши уравнения

а) \(\left(\dfrac{1}{5}\right)^x=125\) ; \(x=\) [ ];

б) \(6^{3x-4}=36\) ; \(x=\) [ ];

в) \(\log\_7 x=-2\) ; \(x=\) [ ];

г) \(\log\_\frac{1}{5} (4x-1)=-1\) ; \(x=\) [ ].