When making a 1L 1X PBS solution from the stock 10X concentration, how would you do it; which formula would you use?

Your interviewer will ask situation- and knowledge-based questions to understand how you outline your process and how well you can explain concepts to others. In this case, buffers and reagents come at concentrations that may or may not be suitable for direct use. This is a standard calculation used routinely as a Research Associate. Remember, you do not need to ask what PBS is as it's irrelevant to the result, and it's a common reagent in most laboratories.