△BAE and △BDE are on the same base BE and between the same parallel BE and AD.
∴ Area of △BAQ=Area of △BDE [two triangle on the same base and between the same parallel are equal in areas] (I)
△BCE and △BEF are on the same base BE and between the same parallel BE and CF.
∴ Area of △BCE=Area of △BEF [two triangle on the same base and between the same parallel are equal in areas] (II)
Adding the corresponding sides (i) and (ii) we get,
Area of △BAQ+Area of △BCE=Area of △BDE+Area of △BEF
=>△AEC=△DBF