Question 493840
It actually doesn't have a defined slope.  If you remember, slope is the change in y value over the change in x value.  Notice that our y values are changing, but our x is stuck on this one value 12.   So we have   y2-y1 / 12-12  -->  y2-y1 / 0. We cannot ever divide by 0 in mathematics. So the slope for any vertical line, that is x = [insert some number], is UNDEFINED.