Answer
(a) $x=\dfrac{1}{9}$
(b) $x=3$
Work Step by Step
RECALL:
$\log_b{x}=y \longrightarrow b^x=y$
Use the rule above to obtain:
(a)
$\begin{array}{ccc}
&3^{-2}&=&x
\\&\dfrac{1}{3^2}&=&x
\\&\dfrac{1}{9}&=&x
\end{array}$
(b)
$\begin{array}{ccc}
&5^x&=&125
\\&5^x&=&5^3
\end{array}$
Use the rule $a^m=a^n \longrightarrow m=n$ to obtain:
$x=3$