Answer
(a) $f(4)=81$
(b) $g(9)=2$
(c) $f(-2)=\frac{1}{9}$
(d) $g\left(\frac{1}{27}\right)=-3$
Work Step by Step
(a) Substitute $4$ to $x$ in $f(x)$ to obtain:
\begin{align*}
f(4)&=3^4\\
f(4)&=81
\end{align*}
(b) Substitute $9$ to $x$ in $g(x)$ to obtain:
\begin{align*}
g(9)&=\log_3{9}\\
g(9)&=\log_3{(3^2)}\\
g(9)&=2
\end{align*}
(c) Substitute $-2$ to $x$ in $f(x)$ to obtain:
\begin{align*}
f(-2)&=3^{-2}\\\\
f(-2)&=\frac{1}{3^2}\\\\
f(-2)&=\frac{1}{9}\\\\
\end{align*}
(d) Substitute $\frac{1}{27}$ to $x$ in $g(x)$ to obtain:
\begin{align*}
g\left(\frac{1}{27}\right)&=\log_3{\left(\frac{1}{27}\right)}\\\\
&=\log_3{\left(\frac{1}{3^3}\right)}\\\\
&=\log_3{\left(3^{-3}\right)}\\\\
&=-3
\end{align*}
