I can give you are summary of how to do it. UK geometry is somewhat different to US with regard to symbols used and names.
You need to prove that the 2 triangles BCE and ADE are congruent and then you can say that the sides are also congruent:- Sides BC and AD are equal (opposite sides of a parallelogram) Also < CBE = <ADE ( alternate angles) and < BCE = EAD ( alternate angles) So the triangles are congruent by 2 angles and the corresponding side, ( I think that would be ASA in the US).
