First, I need to recall James Stewart's precalculus textbooks. He's known for his calculus textbooks, but he's also authored precalculus ones. The 6th edition might refer to the book "Precalculus: Mathematics for Calculus" by James Stewart, Lothar Redlin, and Saleem Watson. The user might be referring to that one. I should confirm if that's the correct book, but given the information, it's the most likely one.