Hello, I am using the Nelson- Principles of Mathematics 12 to teach Math 30-2. On page 94 , question 15  we work through solving permuation equations solving for n and r. On page 119 there are combination questions to solve each combination equation  for either n or r. I do not see much in the book on these topics but did find multimedia clips on the Learn ALberta site for solving permuation equations for n and r. Do you cover the finding of n or r with the combinations with your students?