[tex]\bf (\stackrel{x_1}{-3}~,~\stackrel{y_1}{-8})\qquad (\stackrel{x_2}{-12}~,~\stackrel{y_2}{-20}) \\\\\\ \stackrel{slope}{m}\implies \cfrac{\stackrel{rise} {\stackrel{y_2}{-20}-\stackrel{y1}{(-8)}}}{\underset{run} {\underset{x_2}{-12}-\underset{x_1}{(-3)}}}\implies \cfrac{-20+8}{-12+3}\implies \cfrac{-12}{-9}\implies \cfrac{4}{3}[/tex]
