How do I find a counterexample in order to disprove (A∪B) ⊕(C∪D) ⊆ (A∪C) ⊕(B∪D)?

Answer 1

Let x be an element in (A intersect C) - ( b U d)

then x is an element of A and C but Neither b nor D.

So then x is and element of A U b as well as c U d, so the left side is satisfied.

since x is in nether B nor D, x is NOT an element in b U D, so the right side

does not follow

Use a venn diagram