If U is the universal set {1 , 3 , 5 , 7 , 9 , 11} , A is a subset {1 , 3 , 7 , 11} and C is a subset {3 , 7 , 11} . B is a subset {3 , 5 , 7 , 9} . Use the subsets to verify that A n [ B n C ] = [ A n B ] n C . What property is this ?