A differential equation is one that contains the derivative of a function. For example f(x) + 3 = 4f'(x) - 2. Usually you will be given one of the functions and initial conditions if you have to solve.
Well it shows that the main cube is 9 blocks tall. It is a perfect cube, not a rectangular prism or anything, so every side is the same. So 9 cubed. Or, in other words, 9*9*9
300
divide 3000 by 10 to get a tenth of 3000