[tex](\stackrel{x_1}{20}~,~\stackrel{y_1}{-7})\qquad (\stackrel{x_2}{10}~,~\stackrel{y_2}{-2}) \\\\\\ \stackrel{slope}{m}\implies \cfrac{\stackrel{rise} {\stackrel{y_2}{-2}-\stackrel{y1}{(-7)}}}{\underset{run} {\underset{x_2}{10}-\underset{x_1}{20}}}\implies \cfrac{-2+7}{-10}\implies -\cfrac{1}{2}[/tex]
[tex]\begin{array}{|c|ll} \cline{1-1} \textit{point-slope form}\\ \cline{1-1} \\ y-y_1=m(x-x_1) \\\\ \cline{1-1} \end{array}\implies y-\stackrel{y_1}{(-7)}=\stackrel{m}{-\cfrac{1}{2}}(x-\stackrel{x_1}{20}) \\\\\\ y+7=-\cfrac{1}{2}x+10\implies y=-\cfrac{1}{2}x+3[/tex]
