Step 1
use distributive property
[tex]\begin{gathered} 3\left(4x+6\right)=9x+12 \\ 12x+18=9x+12 \end{gathered}[/tex]Step 2
move all terms with x in the left, and the numbers in the rigth
[tex]\begin{gathered} 12x+18=9x+12 \\ 12x-9x=12-18 \\ 3x=-6 \\ \end{gathered}[/tex]Step 3
divide each side by 3
[tex]\begin{gathered} 3x=-6 \\ \frac{3x}{3}=\frac{-6}{3} \\ x=-2 \end{gathered}[/tex]so,the answer is -2