Answer
$\color{blue}{4}$
Work Step by Step
RECALL:
(1) $a^m \cdot a^n = a^{m+n}$
(2) $\dfrac{a^m}{a^n} = a^{m-n}$
(3) $a^{1/n} = \sqrt[n]{a}$
(4) When $n$ is odd, $\sqrt[n]{a^n}=a$
Use rule (2) above to obtain:
$=64^{5/3-4/3}
\\=64^{1/3}$
Use rule (3) above to obtain:
$=\sqrt[3]{64}
\\=\sqrt[3]{4^3}$
Use rule (3) above to obtain:
$\\=\color{blue}{4}$
