LG Open Assignment Question

[John]

On page 212 of the LG book, I'm failing to see how they are making the statement that "if Mendel and Nastassia can't share any food, Nastassia can't get a pretzel and kebab". I'm reading the the statement given as "Mendel does not buy any kind of food that Nastassia buys". so if Nastassia buys Fruit and a Hot Dog, Mendel wouldn't buy those. I don't see the reverse being true from the statement. What am I missing?

(I can still agree that Nastassia can only buy 2 given it has to be either a Hot dog or Shish Kebab) just don't understand their statement.

[timmydoeslsat]

On page 212 of the LG book, I'm failing to see how they are making the statement that "if Mendel and Nastassia can't share any food, Nastassia can't get a pretzel and kebab". I'm reading the the statement given as "Mendel does not buy any kind of food that Nastassia buys". so if Nastassia buys Fruit and a Hot Dog, Mendel wouldn't buy those. I don't see the reverse being true from the statement. What am I missing?

(I can still agree that Nastassia can only buy 2 given it has to be either a Hot dog or Shish Kebab) just don't understand their statement.

You are making two slight mistakes.

First, Nastassia could not have an S. This is because we know the M has an S.

M and N cannot share any food in common, thus there is no way that N could have S.

Second, the reverse of the statement "M does not buy anything that N buys" also means that N cannot buy anything that M buys.

This is because if N were to buy something that M has, that is breaking the rules. At that point M would have an item in common with N.

I hope that answered your question. If not, please say so.