Three families celebrate Thanksgiving together: Alvarados, the Bells, and the Carsons. There are four people in each family. Afterward, they line up for a large group photo. How many ways can the 12 of them line up?
The families are distinguishable, the people in the families are indistinguishable.
So we have to arrange four As, four Bs, and four Cs.
12!/(4!*4!*4!) = 34650