Answer: Babs and Yabu also eat at Quonk!
Surprised? If not your logic is excellent! Most people think no other pair eat at Quonk. The Vulcans would be proud of you if you got it right! Why is that the answer?
We know Alice and Zach eat together at Quonk. That means that EITHER
It is not BOTH Alice and Zach who like to eat there as then they would have eaten somewhere else.
This means that the woman and man in question is EITHER
We cannot tell which though. Luckily, that does not matter, we have enough information. In both cases we get the same conclusion.
If it is Alice and Yabu that like Quonk, then:
If it is Babs and Zach that like Quonk then:
So whichever the pair is:
Did that make your brain ache? Dont worry its good for you! The puzzle is actually based on one devised by psychologists to be particularly difficult for Humans (though perhaps not Vulcans). It was used in an experiment aiming to show that our brains are wired to naturally think illogically in some ways! Because of that it is very counter-intuitive for us that the answer doesnt have to have either Alice or Zach in.
If you are reading this because of trying to answer the questions in BrainAcademy 2005 and searching for the answer to the logic puzzle question, then you should have realised by now that this is basically the same puzzle set in a different situation. The logic of the answer is the same. Either work it through for yourself for the BrainAcademy version, or just substitute the appropriate names for shapes/colours.