[tex]\begin{gathered} 3(m+7)\leq-15 \\ 3m+21\leq-15 \\ 3m+21-21\leq-15-21 \\ 3m\leq-36 \\ \text{divide both sides by 3} \\ \frac{3m}{3}\leq\frac{-36}{3} \\ m\leq-12 \end{gathered}[/tex]
The mistake was the inequalities sign that was changed .The inequality sign is not suppose to be greater than or equal to but it should be less than or equal to.
