Add '15' on both LHS and RHS of the above expression.
[tex]\begin{gathered} 6x-15+15=-153+15 \\ 6x+0=-138 \\ 6x=-138 \end{gathered}[/tex]Divide RHS and LHS of the above expression with six.
[tex]\begin{gathered} \frac{6x}{6}=\frac{-138}{6} \\ x=-23 \end{gathered}[/tex]Thus, the value of x is -23.
