1) Because [tex]\angle ACB[/tex] is a central angle, [tex]m\angle ACB=72^{\circ}[/tex].
Since [tex]\angle ACB[/tex] and [tex]\angle BCD[/tex] are supplementary, they form a linear pair, and thus [tex]m\angle BCD=180^{\circ}-72^{\circ}=\boxed{108^{\circ}}[/tex]
5) Tangents drawn from an external common point are congruent, so CR=CP=8 and RB=BQ=4. This means that QA=11, and so PA=11 as well. Adding CP+PA, we get AC=19.
6) By the inscribed angle theorem, angle QPR measures 36 degrees.
