Answer
{$\frac{1}{3}$}
Work Step by Step
For all positive numbers $a$, where $a\ne1$, and all positive numbers $x$, we know that $y=log_{a}x$ means the same as $x=a^{y}$.
Therefore, $x=log_{125}5$ means the same as $125^{x}=5$.
We know that $x=\frac{1}{3}$, because $125^{\frac{1}{3}}=\sqrt[3] 125=5$.