Answer :

luana
[tex]12n+9=6-3n\ \ \ \ \ \ |Add\ 3n\ to\ each\ side\\\\ 15n+9=6\ \ \ \ \ |Subtract\ 9\\\\ 15n=-3\ \ \ \ \ |Divide\ by\ -15\\\\ n=-\frac{3}{15}=\boxed{-\frac{1}{5}}[/tex]