[tex]\bf \begin{array}{ccccccccc}
&&x_1&&y_1&&x_2&&y_2\\
% (a,b)
&&(~ 1 &,& h~)
% (c,d)
&&(~ 2 &,& -7~)
\end{array}
\\\\\\
% slope = m
slope = m\implies
\cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{-7-h}{2-1}=\stackrel{slope}{-9}\implies \cfrac{-7-h}{1}=-9
\\\\\\
-7-h=-9\implies 2=h[/tex]
