Hint: Find the probability that all six can't go.
Edit: The answer to the original question depends on whether it's "exactly one" or "at least one".
Zane's favorite rock group is in town this coming weekend, and his parents
have offered to take him and a friend to the concert. Zane knows that six
of his friends would like to go. However, at this late date, he figures that
the chance of anyone he invites being free to go is slim. What is the
probability that one of Zane's friends will be able to accept his invitation?
Please help me!!!