Answer:
see image
Explanation:
use a ruler and a "set square", a tool to make a neat 90° angle. See image.
Point R can be anywhere as long as it is not on PQ. PQ can be at any angle or any length. There are many, many ways to follow these directions. The idea maybe be to practice using the tools or the idea may be that for any segment and point not on the segment, there exists a way to drop a perpendicular from the point to the segment.