You may come across the situation where you already get questions from members of your audience before you start your presentation. Based on the invite you may receive questions or even during the event where you need to present you may have people approaching you with questions. You can manage this situation in different ways.
Obviously you can answer the question directly, but this would mean that you have to repeat yourself during the presentation again as the others attendants have not heard the answer. What you could do is say that you could answer the question directly but you prefer to address it during the presentation. You can then ask the person if he/she would be comfortable to ask the question again during your presentation. If you can remember the name of the persons you may refer to him / her during your presentation. For example “<name>, you asked me a question about this topic before the presentation. Would you mind to repeat the question so that others know what you were wondering about”. By means of this you enforce some nice interaction with your audience and other questions may also be raised by your audience so you can address all that they want to know.
The book that is part of the Public Speaking Kit includes a section with tips and tricks about how to address questions from your audience (even if you don’t know the answer).