Hello. I guess that you failed to read the guidelines for this forum. The main rule is that you need to post a clear question (which you did) and show your work so we know exactly where you are stuck. Are you stuck at the beginning, the middle, the end...? There are many methods to use to solve problems and if you show us your work then we will know the method you want to use and can then guide you to the solution.
Have you learned the hypergeometric method?