In how many ways can 10 people be seated IN A ROW if there a

In how many ways can 10 people be seated IN A ROW if there are four married couples and each husband must sit next to his wife?

Solution

consider 4 married cuples as a single entry people as they are sitting in next to his wife and 2 people are 2 entry

so there are 6 entry ( 4 couples+2people) the can arrange in 6!=720 ways