2. I shall add a diagram to go along with the explanation. The known vertices are (2,7) (8,7) and (2,9). To find the fourth vertex of the rectangle, you have to find the common coordinates. The y-coordinate 7 is common in both (2,7) and (8,7), meaning they are two end points on one line. The x-coordinate 2 is common in both (2,7) and (2,9), meaning they also are two end points on one line, and that (2,7) is the one corner we know of. The other corner also has to have a common number. Because we need it to have a common x-coordinate and a common y-coordinate in order to make it a rectangle, the fourth vertex will have the coordinates of (8,9).11. The point M (x, y) is reflected over the x-axis. Reflecting something over the x-axis means that the y-coordinate becomes the opposite (positive to negative, negative to positive), but the x-coordinate stays the same. This means that the answer would be choice D (x, y) ⇒ (x,-y)