Answer :
[tex]12-3(2w+1)=7w-3(7+w) \\ \\ 12-6w-3=7w-21-3w \\ \\ 9-6w=4w-21 \\ \\ -6w-4w=-21-9 \\ \\ -10w=-30 \\ \\ \boxed{x=\frac{-30}{-10}=3}[/tex]
[tex]12-3(2w+1)=7w-3(7+w)\\\\
12-6w-3=7w-21-3w\\\\
-6w-7w+3w=-21-12+3\\\\
-10w=-30\ \ \ |Divided\ by\ -10\\\\
w=3\\\\ \textbf{Answer\ is\ w=3.}[/tex]