If Juan went to the party, it is highly unlikely that Maria would have enjoyed the party.
Evidence
If Juan went to the party, it is JW → ~ME highly unlikely that Maria would have enjoyed the party.
But in fact it turned out that Maria ME did enjoy the party.
Conclusion
It is highly likely that Juan was at ~JW [went] the party.
Evaluate
This argument contraposes the first premise and is a valid argument.