Q. if A is proper subset of B i.e A⊂B then is it true -
that B⊆A
Ans. No , Never since Ais proper subset hence B is Strictly greater(superset) than A niether equal nor smaller(subset)
Q. A⊂B then AUB = A where U means UNION
A. No ,Never as you can see a being proper subset is completely inside B so taking union that is all elements of B and A (each element taking only once) will surely give bigger part as the result here it would be B.