Answer
$x=-4$
Refer to the graph below.
Work Step by Step
RECALL:
A vertical line has an equation of the form $x-h$. Every point on the line has an x-coordinate of $h$.
The given line is vertical and passes through the point $(-4, 3)$.
This point has an x-coordinate of $-4$.
Since every point on a vertical line has the same x-coordinate, then the is equation of the given line is $x=-4$.
Refer to the graph in the answer part above.