First getting x as a numerator rather than a denominator. Then grouping like terms by moving 5 from the left side to the right. Work below:
[tex] \frac{1}{5} = \frac{25}{x} \\ \frac{1}{5}*x = \frac{25}{x}*x\\ \frac{1}{5}x = 25\\\frac{1}{5}x * 5 = 25*5\\x=125[/tex]