Probability and combinatorics questions
If there are 20 people with 17 men and 3 women and they seat themselves randomly at 4 Tables (A,B,C,D) with 5 people each. With all arrangements being equally likely, what is the probability that no woman sits at table A ?
I am a little confused as how to being this problem. The total seating arrangements is 20 factorial but I am not sure how to handle duplicates here.