In rectangle ABCD, AB = 18, BC = 24, and AECF is a rhombus. Find FD. The figure is not drawn to scale.
lets call FD x.
18^2+x^2=(24-x)^2
324+x^2=576+x^2-48x
48x=252
x=$\boxed{\frac{21}{4}}$
+592 
