Anytime you have a an equation of a line that is y equals a constant, you have a horizontal line. In this case, it is a horizontal line that is 7 above the x-axis.
Any line that is perpendicular to a horizontal line is a vertical line. The equation for a vertical line is x equals a constant.
The equation for the line you need is : x = 8, because it is the only vertical line that passes through (8,6).
x = 8