The correct answer to puzzle 1, as posed, is not in fact simply 1⁄3, because you’ve got to factor in Pr(you say “I have two children and one is a boy” | each scenario) and it’s not at all clear that these are equal in the BB, BG, GB cases. For instance, if you say that in the ordinary course of events (rather than, e.g., to pose a puzzle) I think BG and GB are very much more likely than BB, because if you had two boys why on earth would you say “I have two children and one is a boy”?
In the correct version of this story, the mathematician says “I have two children”, and you ask, “Is at least one a boy?”, and she answers “Yes”. Then the probability is 1⁄3 that they are both boys.
Indeed, and this exact malformed problem is also discussed in the post “My Bayesian Enlightenment”: