So check it. I have this years chem 31A/B textbook, but had to use the "mastering chemistry" pass-codes that came with it last year. If you buy the text book from me for 50$ and then purchase the "mastering chemistry" pass-codes online (or through the bookstore) for 75$ you'll be saving 28$. Currently a new copy of the chem 31A/B textbook (with MC codes) costs 153$ and a used chem 31A/B book (without codes) costs 113$. So buying this book is great deal. Email for details