For every integer n > 0 there is some real number x > 0 s.t. x < 1/n..

I need a proof. Contrapositive? I don't know what to do.

Thanks.

Another question, too:

A fraternity has a rule for new members: each must always tell the truth or always lie. They know

which does which. If I meet three of them on the street and they make the statements below,

which ones (if any) should I believe?

A says: \All three of us are liars."

B says: \Exactly two of us are liars."

C says: \The other two are liars."