If 12 people are to be divided into 3 committees of respective sizes 3, 4, and 5, how many divisions are possible?

I think that Zegroes answer is correct although I do not understand the explanation that he has given.   

The number of ways that 3 people can be chosen from 12 is   12C3 = 220

There are 9 people left.  The number of ways that 4 people can be chosen from these is 9C4 = 126

There are 5 people left.  The number of ways that 5 people can be chosen from these is 5C5 = 1

so the number of possible committees is 220 * 126 * 1 = 27720

you can choose in a different order if you wish but the answer will be the same.    

27720 committess see just line the 12 people up in one of 12 ways first three are commitee 1 next 4 is commite 2 and the last 5 are commite 3 and the order dosent matter of how you lined it up so!!! 12 /(3 4 5)=27720 commitess or divisions