check the picture below.
[tex]\bf \begin{array}{ccccccccc}
&&x_1&&y_1&&x_2&&y_2\\
% (a,b)
&&(~{{ 0}} &,&{{ 5280}}~)
% (c,d)
&&(~{{ 70}} &,&{{ 11990}}~)
\end{array}
\\\\\\
% slope = m
slope = {{ m}}\implies
\cfrac{\stackrel{rise}{{{ y_2}}-{{ y_1}}}}{\stackrel{run}{{{ x_2}}-{{ x_1}}}}\implies \cfrac{11990-5280}{70-0}\implies \cfrac{6710}{70}\implies \cfrac{671}{7}[/tex]
