prove that (A-B) U (B-A) =(A U B) - (A intersection B)

Let A={a,b,c} & B={a,b,d}

LHS=> A-B={c}  and B-A={d} 

Thus, (A-B) U (B-A)={c,d}

RHS=>  A U B= {a,b,c,d}

A ∩ B = {c,d}

Thus, (A U B) - (A ∩ B) = {c,d}

LHS=RHS

Hope it helps.