Answer :
[tex]4(x+3)=9x+16+3x\\\\
4x+12=9x+16+3x\\\\
4x+12=12x+16\ \ \ | subtract\ 4x\\\\
12=8x+16\ \ \ | subtract\ 16\\\\
-4=8x\ \ \ | divide\ by\ 8\\\\
x=-\frac{1}{2}[/tex]
[tex]4(x+3) = 9x+16+3x\\
4x+12=12x+16\\
8x=-4\\
x=-\frac{4}{8}=-\frac{1}{2}[/tex]