Answer
(a) $\log_8{(\frac{1}{8})}=-1$
(b) $\log_2{(\frac{1}{8})}=-3$
Work Step by Step
RECALL:
$b^y=x \longrightarrow \log_b{x}=y$
Use the rule above to obtain:
(a) $\log_8{(\frac{1}{8})}=-1$
(b) $\log_2{(\frac{1}{8})}=-3$