The Pan Global Thermodynamics materials describe a problem that deals with partial pressures of ideal gases. I found this example and the explanation of the solution to be very confusing. So did a gentleman named Marcel, who asked for clarification in a Facebook Group.
Below I have included a video with a more thorough, and I hope clearer, explanation.
The question is misleading and refers to water and water vapour interchangeably. This sort of wording is often used on exams to trip a person up. The justification being that one must understand that you cannot use a partial pressure analysis for the liquid water therefore the question must be referring to the partial pressure of the water vapour.
I hope that is clear as mud now, if you have further questions that you would like clarified please send an email.
Mike Grossman, P. Eng.