Question 510225
the first person can choose any of 10 seats, this leaves a choice of 9 seats for the other person
___ for a total of 90 possible seating arrangements (9 * 10)


the 10 seats contain 9 adjacent pairs
___ each of those pairs can be occupied in 2 ways (who's on the left and who's on the right)
___ this means 18 seating arrangements are not allowed (9 * 2)


so there are 72 ways for the people to sit (90 - 18)