draw a rectangle and label width x and height y
xy = A is what we are maximizing
However, we only have 600 = 2x + 3y since we have a fence in the middle
solve 600 = 2x+3y for either x or y.
plug that equation into xy = A
Now we have a function A(y) or A(x)
Derive A(y) or A(x) and set the derivative equal to 0, then solve for x or y