Please find attached problem and my work.
I am stuck.
1. Have a look here: Intersecting Chords Theorem
2. The radius of your circle is r = PB = 3. Produce BP until it intersect the circle in F.
3. According to the chord theorem you'll get:
$\displaystyle \overline{FD} \cdot \overline{DB} = \overline{AD} \cdot \overline{DC}$