The question "The probability for a streak when tossing a coin" is on hold. [Edit: It has been reopened.] I disagree with closing the question and voted to reopen.
This problem may sound like it is easy. As far as I know, it is not, even though the comment on the problem and quick closure make it sound like it might be just an exercise. You can set up a recurrence which isn't so easy to analyze, and there is a complicated approximation in Feller's classic book. If there is a simple way to solve this problem that Feller and others have overlooked, I'd like to know about it. I think it would be appropriate to put the recursion and approximation in an answer on MO (others would be better than I would be at writing such an answer), and not push the question to MSE.
I think there is a tendency for people to misjudge the level of combinatorics problems just because they may sound simple. Please be careful when considering whether to vote to close a problem if it is outside your main area of expertise, even if it looks like there are votes to close already.