Answer
$0$
Work Step by Step
$\log_{b}x=y $ is equivalent to $ b^{y}=x.\qquad (*)$
Consequently,$\qquad \log_{b}b^{x}=x.\qquad (**)$
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First,
$\log_{8}8=\log_{8}8^{1}\stackrel{(**)}{=}1$
and,
$\log_{3}(\log_{8}8)=\log_{3}(1)=\log_{3}3^{0}\qquad $.... apply (**)
= $0$
