question #18 under unit 1 practice questions gives a value of 12.90 ohms for the value of K. I'm sure it's obvious but I do not know how how to find that value, or I have forgotten please help.
We have no way of knowing what book you are getting your practice questions from. A lot of companies publish practice exam books. So I cannot be sure what "K" means, in the context of that book. Can you be more specific?