Okay, let's try some example sets. I am assuming Ac is complement or anything not in A. I believe you write the elements of the set in braces. I'm a bit rusty at this, but I have done tons of math in my life.

B {all orange things}

A {all fruits}

B - A = all orange things except orange fruits

Ac {all non-fruits}

B intersection Ac = all orange things THAT are not fruits

Does all orange things except orange fruit = all orange things that are not fruit?

No: there is your answer :D. I hoped that helped! Let me know if you have any troubles with this logic.