In circle Q with m PSR = 18, find m PQR.

From the figure:
[tex]\begin{gathered} m\angle PSR=\frac{PR}{2} \\ so\colon \\ 18=\frac{PR}{2} \\ PR=2\cdot18 \\ PR=36 \end{gathered}[/tex]therefore:
[tex]\begin{gathered} m\angle PQR=PR \\ m\angle PQR=36 \end{gathered}[/tex]