posted by mandeep .
Let A, B and C be the sets such that A ∪ B = A ∪ C and A ∩ B = A ∩ C.
Show that B = C.
you can easily prove oit with a Venn diagram.
If not: A¾B=A+B-A¿B=A+B-A¿C
As AUB=AUC then A+B-A¿C=A+C-A¿C hence; B=C