You can put this solution on YOUR website! (0,5)(-3,-4) developes the slope of
(y2-y1)/(x2-x1)
(-4-5)/(-3-0)
-9/-3=3 is the slope of a line through these 2 points.
for a perpendicular line it has to have a slope of -1/3 (this is a negative reciprical of the line with the slope of 3).