Question 1075497
Level 1; x and 10+x-12=x and x-2, and that area is x^2-2x.
Level 2: x(x-12)=x^2-12x
Total area is their sum: 2x^2-14x
When x=20, the area is 2*20^2-14(20)=520 ft^2.
520/400=1.3 gallons.