Well we know that...[tex]a^{-1}=\frac{1}{a^{1} }\\[/tex].
So...[tex](\frac{1}{5})^{-1}=\frac{1}{\frac{1}{5}^{1}}=5\\\\[/tex].
Because [tex]5^{3}=125[/tex],
[tex]\frac{1}{5}^{-1*3}=125\\ x=-1*3=-3[/tex]
answer: -3