Answer
$x=-6$
Work Step by Step
$$\begin{align*}
3(x+1)+6-6&=-9-6 &\text{Subtract 6 from each side.}\\
3(x+1)&=-15 &\text{Simplify.}\\
\frac{3(x+1)}{3}&=\frac{-15}{3} &\text{Divide 3 to both sides.}\\
x+1&=-5 &\text{Simplify.}\\
x+1-1&=-5-1 &\text{Subtract 1 from each side.}\\
x&=-6 &\text{Simplify.}
\end{align*}$$
Check the answer by substituting $-6$ to the variable $x$ in the given equation.
$$\begin{align*}
3(x+1)+6&=-9\\
3(-6+1)+6&\stackrel{?}{=}-9\\
3(-5)+6&\stackrel{?}{=}-9\\
-9&\stackrel{\checkmark}{=}-9
\end{align*}$$
Thus, the solution is $x=-6$.
