Answer
$8$
Work Step by Step
Using $a^{m/n}=\sqrt[n]{a^m}=(\sqrt[n]{a})^m$, the given expression, $
64^{1/2}
,$ is equivalent to
\begin{array}{l}\require{cancel}
\sqrt[]{64^1}
\\\\=
\sqrt[]{64^1}
\\\\=
\sqrt[]{(8)^2}
\\\\=
8
.\end{array}