Answer
$\quad \log_{64}16=2/3.$
Work Step by Step
For $x\gt 0$ and $a$, a positive constant other than 1,
$\log_{a}x$ is the exponent to which $a$ must be raised in order to get $x$.
Thus, $\log_{a}x=m$ means $a^{m}=x$
Here, $ 64^{2/3}=16 \quad$ means $\quad \log_{64}16=2/3.$
