I assume that it is about the todo list in chapter 4, and that you are using eclipse (as i do).
It seems that your gen/R.java has been corrupted.
Sometimes only changing the min sdk value in the manifest does not solve all problems..
Important is to check the properties for the project, at least the android project build target, that should be android 3.0 (api level 11).
If that is ok, go back to the project home screen. File/Refresh the whole project
If the errors are still there, rebuild the project with the "clean" submenu in the "project" pull down menu. That will also rebuild the R file.
If that does not help,
try android tools menu (right mouse click on the project name in the package explorer, then run Lint, and see what is still not ok.
Hope this helps!