Evaluate: 3x-9 <-18

Expression: $3x-9 < -18$

Move the constant to the right-hand side and change its sign

$3x < -18+9$

Calculate the sum

$3x < -9$

Divide both sides of the inequality by $3$

$\begin{align*}&x < -3 \\&\begin{array} { l }x \in \langle-\infty, -3\rangle\end{array}\end{align*}$