See the attached picture to better understand the problem we know that in rectangle ABCD AB=CD and AD=BC therefore the triangle ACD and triangle ABC are congruent so BD=AC BD=8 units
the answer part a) is BD= 8 units
Part b) Find angle CBD
we know that ∠ABD+∠CBD=90°---------> by complementary angles so ∠CBD=90-∠ABD-----> 90-67----> 23° ∠CBD=23°