You take 64 miles for 2 gallons and divide it by 2. And it leads up to 32 miles and 1 gallon. Now you divide that by 2 again and get 16 miles and 1/2 gallon. So, to check that you can take 16+16 and you get 32 and take 32+32 and you get 64.
The area of a triangle is 1/2(base)(height) and since this is a right triangle the two legs can be base and height. So the area is 1/2(2x-4)^2 which becomes 1/2(4x^2-16x+16) which is simplified to 2x^2-8x+8. B is the correct answer.
