An Angle Bisector in a Parallelogram Question

Question & Solutions are in image below except the (a) part whose solution is as follows:

EAB = 1/2(BAC)

And

EBA = 1/2(DBA)

So

EAB + EBA
= 1/2(BAC + DBA)
= 1/2(180)
= 90

*Note: EBA = angle (EBA)

So for (a), we write:

AEB
= 180 – (EAB + EBA)
= 180 – 90
= 90