Jeans Paradox

This puzzle is from the "Ask Marilyn" column in the 3/4/2012 issue of "Parade" magazine:

A girl wants a pair of jeans that cost $97 and borrows $50 each from two friends. She buys the jeans and gets $3 back. She gives each friend $1 and keeps $1.

Now the girl owes her friends $49 apiece. But $49 plus $49 is $98; when you add the $1 she kept, you get $99.

Where's the missing dollar?

Please click here for the answer.