Start here: A = 18 ft^2 = L * W. Next, L = 2W.
Merging these 2 formulas lets us eliminate L:
18 ft^2 = (2W) * (W) = 2W^2.
So W^2 = 9 ft^2, and W=3 ft. Please use L = 2W (from above) to calculate L.
Volume of jupiter: 1.43×10^15cubic kilometers
volume of earth: 1.08×10^12 cubic kilometers