See its a tricky question :
1) we have 12 different books to be send into packets having same address ----> means n distinct objects to be placed into r identical boxes.
2) now 3 of them contains 3 each and one among them has atleast 2.
means possible combinations {3,3,3,3} only .
one among them has atleast two books is a dead statement // it has no reference for question //given only to confuse
so number of ways : (as parcels are identical they will be selected in one way only)
{3,3,3,3} = 12!/((3!)4*4!) = 15400
#total ways = 15400 ways.