It occurred to me after reading Morris' post that people possess different cognitive abilities and different backgrounds with respect to understanding logic. For that reason, I will break this riddle down a little.

Remember, the members of one religion always tell the truth and the members of the other religion always tell a lie. The question to ask a member of either religion is this:

"If I consult the scriptures of the religion you don't belong to which path I should take to get to G-d, what would those scriptures say?"

If one asks a Jew how the xtian scriptures say to get to got, the Jew will answer that according to xtian scriptures, the GT says the way to get to G-d is through J'sus.

On the other hand, if one asks a xtian how the Jewish scriptures say to get to G-d, the xtian will say that the Jewish scriptures way to get to G-d through J'sus. In fact, that is the point of xtianity.

Xtianity maintains that the Jewish scriptures, upon which they claim the GT is based, support the teaching of the GT that J'sus is the way to G-d. Remembering that one religion always lies and that the other religion always tells the truth, by taking the opposite path of the advice that the Jew says would be given by the xtian scriptures (GT), or the advise the the xtian claims would be given by the Hebrew scriptures, one will find the true path.