y = 7
x = 4 is a vertical line parallel to the y- axis passing through all points with an x- coordinate of 4
A line perpendicular to x = 4 will be a horizontal line parallel to the x- axis with equation y = c where c is the value of the y- coordinate the line passes through.
line passes through (5 , 7) with y- coordinate 7
The equation is therefore y = 7
