Answer
$x=25$
Work Step by Step
Since $y=b^x$ is equivalent to $\log_b y=x,$ then the given equation, $
\log_x 5=\dfrac{1}{2}
,$ is equivalent to
\begin{array}{l}\require{cancel}
x^{\frac{1}{2}}=5
.\end{array}
Squaring both sides, then,
\begin{array}{l}\require{cancel}
x=25
.\end{array}