Question 58265
First find the slope of the line through the two given points using: {{{m = (y2-y1)/(x2-x1)}}} where: (x1, y1) = (0, 5) and (x2, y2) = (-3, -4)

{{{m = (-4 - 5)/(-3 - 0)}}}
{{{m = (-9)/(-3)}}}
{{{m = 3}}}

The slopes of lines perpendicular to the given line are the negative reciprocals of slope of the given line.

{{{M = (-1/3)}}}