#### Answer

The slope of this line is undefined

#### Work Step by Step

Through $(8,4)$ and $(8,-7)$
The slope of a line is given by $m=\dfrac{y_{2}-y_{1}}{x_{2}-x_{1}}$, where $(x_{1},y_{1})$ and $(x_{2},y_{2})$ are points through which the line passes.
Substitute the points given into the formula and evaluate:
$m=\dfrac{-7-4}{8-8}=\dfrac{-11}{0}=$ undefined