Answer
$2^{-3}=\displaystyle \frac{1}{8}$
Work Step by Step
From the definition of logarithms,
for $a>0$, $a\neq 1$, and $x > 0$,
$y=\log_{a}x$ means $a^{y}=x$.
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$-3=\displaystyle \log_{2}(\frac{1}{8})\ \ $ means $\ \ 2^{-3}=\displaystyle \frac{1}{8} $.