1. The problem statement, all variables and given/known data I am stuck on this problem relating to permutations: The first part asks how many ways can 6 people be lined up. This answer, I believe is 6! = 720 ways. The second part: If 3 specific persons, among 6, insist on following each other, how many ways are possible? The third part: If 2 specific persons, among 6, refuse to follow each other, how many ways are possible? The first part is easy, but I don't know how to do the second and third parts. What is the concept involved in solving the second and third parts? Thanks for the help!