Algebra
posted by Michelle .
(1,4) and (5,8) is (x1,y1) and (x2,y2). The slope is m=(y2y1)/(x21). Substitute and evaluate to find the slope.

Just do what it says ....
m = (84)/(5  (1))
=
finish it up.
btw, your formula conains a typo, should say
m = (y2y1)/(x2x1)