y= -8 is a perfectly horizontal line with a slope of 0. This line goes through the coordinate (every x value, -8). In other words, every x value in the world (rational, that is) will have a y value of -8. -8 is the y coordinate, so our new line has to go through the y coordinate of the given point (-9, 0). The line y = 0 is parallel to the line y = -8.