A rectangular box is 20 cm high and twice as long as it is wide. If it has a surface area of 1600cm^2, what is its volume?
draw a diagram of the box. label the height, length and width as i told you, and just find the area of each face. the top the bottom and all the sides. each side is a rectangle, so the area is just the length times width of the rectangle. then add them all up and set it equal to 1600 to solve for x