# Math Help - Proof these sets...

1. ## Proof these sets...

I have try a couple of time but I can't understand these problems.

2. Originally Posted by aRTx
I have try a couple of time but I can't understand these problems.

For a), let $A=\{1,2,3\}$ , $B=\{3\}$, $C=\{1, 2\}$, then:
$A \cup B = B \cup C = \{1,2,3\}$
but $A \ne B$