I need to simplify these boolean expressions.

1. The problem statement, all variables and given/known data

Problem A:

Problem B:

Problem C:

2. Relevant equations

abc means a AND b AND c
a+b means a OR b
a` means NOT a

I have been working on these for over 6 hours and I still have a mess. I look at the rules and try to apply them, but I know my answers are incorrect.