Answer:
Because AC = BC
=> ️ACB is a isosceles triangle at C
=> m<A = m<B = 71°
At triangle ABC
m<A + m<B + m<ACB = 180°
=> 71° + 71° + m<ACB = 180°
=> m<ACB = 38°
We have m<ACB and m<ECD are 2 opposite angle
=> m<ECD = m<ACB = 38°
At triangle ECD
m<ECD + m<E + m<D = 180°
=> 38° + 90° + m<D = 180°
=> m<D = 52°