Answer :
To solve this using the distributive property you multiply the term oit the parenthesis by the terms in the parenthesis:
[tex]\begin{gathered} -3(a+5)=30 \\ \\ -3\cdot a-3\cdot5=30 \\ \\ \\ -3a-15=30 \end{gathered}[/tex]Then, to solve a you:
add 15 in both sides of the equation:
[tex]\begin{gathered} -3a-15+15=30+15 \\ \\ -3a=45 \end{gathered}[/tex]Divide both sides of the equation into -3
[tex]\begin{gathered} \frac{-3}{-3}a=\frac{45}{-3} \\ \\ a=-15 \end{gathered}[/tex]Then, a is -15