Can someone help me with the following:
see the attachment.
I am really stuck and do not know were to start
(I'm not vulnerable to macro virus's but I don't like opening word and excel attachments because it takes a long time to boot up OOO on my slow computers (I won't open an office document on the my work computers as a matter of principle)
Alternativly one may observe that it is the sum of the number of ways of choosing a subset of elements from the given set which does not include , and the number of ways that does include .
Which is what we expect.
Now the number of ways of choosing a subset that does not contain is , and so the probability required is:
Similarly if is in the set the number of ways of choosing it is