This article is from the Puzzles FAQ, by Chris Cole firstname.lastname@example.org and Matthew Daly email@example.com with numerous contributions by others.
How many flowers do I have if all of them are roses except two, all of
them are tulips except two, and all of them are daisies except two?
There are two solutions:
Three flowers: rose, tulip, daisy
Two flowers: carnation, geranium