Click here to read the complete problem statement.
No use angle chasing, think about perpendiculars and areas. (yes, DE ⊥ AC, but OP forgot to clarify it.)
That simplifies it so much. I quit this problem after hours of trying (Not considering DE to be perpendicular) Thank you.
Ami try kore ans ber korsi, ** but bujhtesi na je eita kivabe aslo mane area theke height jeta CF kintu okhane toh variable asei? Height hoy 7x/3
Thank youuuuuuu 
helped me