Answer
$30^{\circ}$
Work Step by Step
We can see that $\angle APB$ and $\angle APD$ shows complimentary angles, so their sum will be equal to $90^{\circ}$.
We need to find $ \angle APD$
$ \angle APD+60^{\circ}=90^{\circ}$
or, $ \angle APD=90^{\circ}-60^{\circ}=30^{\circ}$
