A politician in a television interview can sometimes get away with giving an answer to a different question than the one that was asked her. Or filling time with some meaningless generic statements, after which a smile indicates that she is ready for the next question.
In a VC fundraising pitch (or an interview for a position) this does not work. If you think you need more time to get to an answer, think before speaking. You cannot parallel process coming up with an answer and speak coherently (both will be bad). If you hope that by repeating something what you said before you might manage to skip the difficult question, it will just bore the VC and make her impatient.
Sometimes it might be best to admit that you do not know or do not want to disclose it.