#### Answer

$\text{exponential growth;}$
$y$-intercept = $\dfrac{7}{8}$

#### Work Step by Step

Recall:
The exponential function $y=c \cdot b^x$ involves exponential:
(i) growth when $b\gt 1$
(ii) decay when $0 \lt b \lt 1$
The given exponential function has $b=18$, which is greater than $1$, therefore it involves exponential growth.
The $y$-intercept of a function can be found by setting $x=0$ then solving for $y$.
Set $x=0$ then solve for $y$ to obtain:
\begin{align*}
y&=\frac{7}{8}\left(18\right)^x\\\\
y&=\frac{7}{8}\left(18\right)^0\\\\
y&=\frac{7}{8}(1)\\\\
y&=\frac{7}{8}
\end{align*}
Thus, the $y$-intercept is $\dfrac{7}{8}$.