Answer
The symbolic form of the provided argument is:
\[\begin{align}
& \left( p\wedge q \right)\to r \\
& \frac{q\wedge \sim r}{\therefore \,\sim p} \\
\end{align}\].
It is a valid argument, where the simple statements are p as the graduate was shown,q as midnight cowboy was shown and r as performance was sold out.