The points (3, -9) and (3, -2) are plotted on a four-quadrant grid. Enter the distance between them in units.

توضیح

The two points share an x-coordinate, so the gap runs straight along the y-axis direction, and both lie beneath the x-axis, nine units down and two units down. The nearer point stands seven units above the deeper one, whereas adding the two depths would only make sense if one of them lay above that axis.