\displaystyle \tt 8-40-15x=13\\
\displaystyle \tt -32-15x=13\\
\displaystyle \tt -15x=13+32\\
\displaystyle \tt -15x=45\\
\displaystyle \tt x=\frac{45}{-15}\\
\displaystyle \tt \underline{\bold{x=-3}} " alt=" \displaystyle \tt 8-5(8+3x)=13\\
\displaystyle \tt 8-40-15x=13\\
\displaystyle \tt -32-15x=13\\
\displaystyle \tt -15x=13+32\\
\displaystyle \tt -15x=45\\
\displaystyle \tt x=\frac{45}{-15}\\
\displaystyle \tt \underline{\bold{x=-3}} " align="absmiddle" class="latex-formula">