Answer
$-5\lt n \lt 4$
The graph is shown below.
Work Step by Step
The given inequality is
$\Rightarrow -6\lt 3n+9 \lt 21 $
Subtract $9$ from each expression.
$\Rightarrow -6-9\lt 3n+9-9 \lt 21-9 $
Simplify.
$\Rightarrow -15\lt 3n\lt 12 $
Divide each expression by $3$.
$\Rightarrow \frac{-15}{3}\lt \frac{3n}{3} \lt \frac{12}{3}$
Simplify.
$\Rightarrow -5\lt n \lt 4$
Hence, the solution is $-5\lt n \lt 4$.
