Answer
Use letters to represent each simple statement in the argument.
p: Metro rail system is in operation.
q: There are traffic delays.
Express the premises and conclusion symbolically as:
\[\frac{\begin{align}
& \sim p\to q \\
& \sim q \\
\end{align}}{\therefore p}\ \ \ \ \ \ \frac{\begin{align}
& \text{If a metro rail system is not in operation, there are traffic delays}\text{.} \\
& \text{Over the past year there have been no traffic delays}\text{.} \\
\end{align}}{\therefore \text{Over the past year a metro rail system has been in operation}\text{.}}\]
The argument is in the form of Contra-positive Reasoning.
Thus, the argument is valid.
