Question: how to answer a question you don't know?
Answer: Repeat or paraphrase the question out loud. ...  Ask clarifying questions. ...  Admit you don't know the full answer. ...  Provide what information you do have. ...  Promise you will find the answer and come back to the questioner. ...  Ask the questioner how to best reach him, if you don't know how. ...  Ask the group to continue the presentation.