x=-3 is an equation that passes through (-3,4) and is perpendicular to y=-2.
Explanation:
The equation y=-2 is going to create a horizontal (slope =0) line that passes through the point (0,-2). To create a line that is perpendicular to that line, you need to create a line that is vertical (no slope).
However, the line also needs to pass through the point (-3,4). so the only equation that works is x=-3.