The question is:

What i have done so far is that i have solved for y where $\displaystyle y= 300-3/2x$. I have also solved the triangle on top of the rectangle where the $\displaystyle h= x(3)^(0.5)$. (its x times root 3)A gable window has the form of a rectangle topped by an equilateral triangle, the side of which are equal to the width of the rectangle. Find the maximum area of the window if the perimeter is 600cm.

I am just not sure what to do from there.

Thank you in advance!