Question

If A ⊂ B, then A ∩ B = A ∪ B.

Answer 1

No. Let A={1,2,3} and B={1,2,3,4}. Then A intersection B is {1,2,3} but A union B is {1,2,3,4}

Answer 2

if \(A\subset B\)

then \(A\cap B=A\) and \(A\cup B=B\)

thus

\[A\cap B\subset A\cup B\]