"To be honest, I do not know the answer either."
Translation:Om eerlijk te zijn weet ik het antwoord ook niet.
Both kennen and weten mean 'to know,' but the main difference is that 'kennen' means to be acquainted with, e.g. people or facts, and it's also a transitive verb, so it needs an object. 'Weten' is used only to refer to facts, and it's also an intransitive verb (with a few exceptions).