Level 6: Construct a parallel line through point C

Hint: A line perpendicular to a perpendicular line is parallel.

Solution: The hint spell out the answer! First, construct a line through C perpendicular to AB. Then construct a line through C perpendicular to the previous line, the line must pass through C, and it must perpendicular to the line perpendicular to AB, so it must be parallel to AB, so we are done.