The coordinates below are the three vertices of a rectangle. identify the fourth coordinate and the area of the rectangle. a.(2,7),28b.(2,7),48c.(7,2),28d.(7, 2),45

The answer is D

This is because the x value of the coordinate has to be the same x coordinate is point c, which means it has to be 7. And the y coordinate has to be the same as point A, which means that the y coordinate has to be 2. 
Leaving the coordinate at (7,2)

Then the area of the rectangle is 45 because when you count the length between points B and C (the length) is 9, and the width (between A and B) is 5. You get 45 by multiplying these values because the area of a rectangle is length times width. 

Just divide the x axis (the top) by 2 or multiply the y axis (the bottom) by 2