其它
Tiffany wants to pack $$9$$ shirts into several bags. There are at least $$2$$ shirts in each bag, and the number of shirts in each bag should be different. There are~\uline{~~~~~~~~~~}~ways to pack the shirts. 
Overseas Competition->Knowledge Point->Counting Modules
$$9=2+7=3+6=4+5$$  $$9=2+3+4$$  So there are $$3+1=4$$ ways 