The equation of a line is typically written as y=mx+b, where m is the slope and b the y-intercept.
The slope can be calculated like this:
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]In this case you have x1=-8, y1=6, x2=-8 and y2=0. Replace this values on the slope formula
[tex]m=\frac{0-6}{-8-(-8)}=\frac{-6}{-8+8}=\frac{-6}{0}\text{ the slope is undefined}[/tex]An undefined slope indicates that you have a vertical line parallel to the y-axis.
This line will pass through all points in the plane with an x-coordinate=constant (c). In this case this constant will be -8
The equation is written in the form x = c, then the equation of this line will be
[tex]x=-8[/tex]