Triangles Questions

In $\Delta ABC$, $AD$ is the internal bisector of $\angle A$, which meets side $BC$ at $D$. If $BD=5\text{cm}$ and $BC=7.5\text{cm}$, then what is the ratio $AB:AC$?

In $\Delta ABC$, $P$ is a point on $AB$ such that $PB:AP=3:4$ and $PQ$ is parallel to $AC$ (where $Q$ lies on $BC$). If $AR$ and $QS$ are perpendicular to $PC$ and $QS=9\text{cm}$, then what is the length of $AR$ (in $\text{cm}$)?