It means that Union of the sets B and C. The "U" means Union of. It denoted as B∪C. Remember that it is a set of all objects member of B, We can also say that it is a set of all objects member of C or both of B and C. B∪C = C∪B.
» (B∪C)∩A'
Let me explain to you this symbol "∩". This "∩" is what we called the intersection. Let me also explain to you this A' means complement. All common elements are in set B and set C or both except in set A.
