x=12 is a vertical line parallel to y axis. It passes through the point x=12. The slope of a line parallel to the y -axis has a slope that is undefined.
x=12 will have undefined slope. Any line perpendicular to x=12 will become parallel to x axis and will have slope =0.
Parallel lines have same slope. Any line parallel to x=12 will have undefined slope.
The line perpendicular to x = 12 will have a slope of 0 and a line parallel will have an undefined slope.
