Answer
The lines are perpendicular because one is a vertical line and the other is a horizontal line.
Work Step by Step
RECALL:
A horizontal line is perpendicular to a vertical line.
The line $y=-3$ contains any point of the form $(x, -3)$, where x is a real number.
This means that the line contains the points (-1, -3), (0, -3) and (1, -3).
Plot these points then connect them using a line.
(refer to the attached image above)
The line $x=-3$ contains any point of the form $(-3, y)$, where y is a real number.
This means that the line contains the points (-3, -1), (-3, 0), and (-3, 1).
Plot these points then connect them using a line.
(refer to the attached image above)
