In how many ways can 12 balls be divided between 2 boys, one receiving 5 and the other 7 balls?
Here order is important, then the number of ways in which 12 different balls can be divided balls can be divided between two boys which contains 5 and 7 balls respectively, is
=12!5!7!×2!
=12.11.10.9.8.7!(5.4.3.2.1)7!×2=1584