to get the slope of any line, we can simply use two points off of it, for this one, say (3,12) and (4,16)
[tex]\bf (\stackrel{x_1}{3}~,~\stackrel{y_1}{12})\qquad (\stackrel{x_2}{4}~,~\stackrel{y_2}{16}) \\\\\\ slope = m\implies \cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{16-12}{4-3}\implies \cfrac{4}{1}\implies 4[/tex]
