Problem with Binomial Coefficients

Hi everybody,

Has somebody any idea why the following is true....?
Attachment 23171

Which rules are applied here?

Thank you very much for any help!

Quote:

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Originally Posted by Marmy

Has somebody any idea why the following is true....? Attachment 23171

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Suppose that we have
If we want to select a committee of can that be done in ways?

Thanks, very helpful again. I think I understand now!