Do you fully understand the inclusion/exclusion principle?
my professor skipped a few lessons in order to make time for the final. in doing that I think he may have avoided teaching this. what's the inclusion-exclusion principle?
my answer was that sum, but without the final term
You must understand the inclusion/exclusion princple to understand the solution.
found it several chapters ahead, thanks. i'll be moving on to my isbn problem which has a thread in the discrete math section. please have a look at it.