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I am having some difficulties on exercise 2e from Topology 2nd ed by J. Munkres . Here are the directions:

determine which of the following states are true for all sets [FONT=MathJax_Math-italic]A[/FONT], [FONT=MathJax_Math-italic]B[/FONT], [FONT=MathJax_Math-italic]C[/FONT], and [FONT=MathJax_Math-italic]D[/FONT]. If a double implication fails, determine whether one or the other one of the possible implication holds. If an equality fails, determine whether the statement becomes true if the "equal" symbol is replaced by one or the other of the inclusion symbols [FONT=MathJax_Main]⊂[/FONT]or [FONT=MathJax_Main]⊃[/FONT].

e.) $A-(A-B)=B$

My work:

Let A={1,2,3,4,5,7} and B={1,3,5,9}

A-B={2,4,7}

A-(A-B)=A-{2,4,7}={1,3,5,9}= B?

Thanks

Cbarker1