Pls EXPLAIN the Q i am not able to understand it. And pls fast

Solution) 
∠ABC = ∠FED (Both 90⁰) ...(1)

∠BAC = ∠EFD (Given)....(2)

The two angles of ΔABC are equal to the two respective angles of ΔFED. Also, the sum of all interior angles of a triangle is 180º. Therefore, third angle of both triangles will also be equal in measure.

So, ∠BCA = ∠EDF ....(3)

Also, given that, BC = ED ...(4)

By using equation (1), (3), and (4), we obtain

ΔABC ≅ ΔFED (ASA criterion)