fragment_main.xml & activity_main.xml

Per the trainers comments in another members question they are working on a solution to address this change however the solution for now is to download the provided environment setup or delete the fragment_main.xml and code referring to it. You'll have to remove the references to each activity being made as fragments are added automatically (unless you use the provided project files/environment).

Check out Ben's reply to this post: https://teamtreehouse.com/forum/the-getsupportfragmentmanager-is-not-a-public-method-of-listactivity

Also, for more on fragments: http://stackoverflow.com/questions/19876874/what-is-the-difference-between-acitvity-main-xml-and-fragment-main-xml-files-in

Overall http://stackoverflow.com/ is a great resource when you run into problems. You're more than likely not the only one running into the issue and this is a resource for asking questions from a community of programmers (new and advanced). As their site says: Stack Overflow is a question and answer site for professional and enthusiast programmers. It's 100% free, no registration required.