If AsubseteqBA \\subseteq BAsubseteqB and BsubseteqAB \\subseteq ABsubseteqA, then:
A=BA = BA=B
AAA is a proper subset of BBB
AcapB=emptysetA \\cap B = \\emptysetAcapB=emptyset
AcupB=UA \\cup B = UAcupB=U