Code:
A     E             B


             X



                    F


D                   C

ABCD there, that's a square.
Be advised that E is on AB and F is on BC.
And YESSSSS, X is on both BD and EF.
You will be relieved after learning that AB = 30.

Now praytell, if EF = DX, please provide yours truly with
the area of triangle BEF.

I'm a man of few words, BUT I use 'em often!!