You're give the bottom line of the rectangle. Then, with the point (96, 1483), you know the final point completing the rectangle has to be at (-52, 1483). Do you see why?

This is one side of the rectangle (length)

This is another side of the rectangle (width).

Now that you're given the length and width, can you find the area? ( )

Another approach would be to find the area of the triangle formed by these 3 points and multiply it by 2. Both ways are just as easy.