#### Answer

$y=4$

#### Work Step by Step

RECALL:
(1) The point-slope form of a line's equation is $y-y_1=m(x-x_1)$ where $m$=slope and $(x_1, y_1)$ is a point on the line.
(2) The slope $m$ of a line that contains the points $(x_1, y_2)$ and $(x_2, y_2)$ is given by the formula $m=\dfrac{y_2-y_1}{x_2-x_1}$.
(3) A horizontal line has an equation of the form $y=k$. Every point on the line has a y-coordinate of $k$.
The line is horizontal so its equation is of the form $y=k$.
The line contains the point $(-7, 4)$, the y-coordinate of which is $4$.
Therefore, the equation of the vertical line is $y=4$.
This equation cannot be written in point-slope form.