Question 452523
Result set for union=∪ holds elements that belong to the either of two sets that make up that union.
:
A ∪ C = {1,2,3,4} ∪ {3,5,7,9} = {1,2,3,4,5,7,9}
:
Result set for intersection=∩ holds elements that are common in both of the sets. 
:
B ∩ (A ∪ C) = {3,4,5,6,7} ∩ {1,2,3,4,5,7,9} = {3,4,5,7}