[tex]\bf (\stackrel{x_1}{3}~,~\stackrel{y_1}{2})\qquad (\stackrel{x_2}{6}~,~\stackrel{y_2}{r}) \\\\\\ \stackrel{slope}{m}\implies \cfrac{\stackrel{rise} {\stackrel{y_2}{r}-\stackrel{y1}{2}}}{\underset{run} {\underset{x_2}{6}-\underset{x_1}{3}}}~~=~~\stackrel{\stackrel{slope}{\downarrow }}{-3}\implies \cfrac{r-2}{3}=-3\implies r-2=-9\implies r=-7[/tex]
