Given are three married couples.
So, let us assume there are 3 men and 3 women
They are sitting in a row of 6 empty seats
There is a definite order constraint that each woman will sit left to her husband. The first woman gets 3 options to choose from 3 available seats. The second woman has two options left as already one seat is filled by the first woman. The last woman has one option left. So, it is [tex]3*2*1[/tex]
So, number of ways is 3! = [tex]3*2*1[/tex] = 6 ways.