12 because dozen means 12.
http://wiki.answers.com/Q/How_many_two_cent_stamps...

in a dozen what? because there are no two cent stamps in a dozen eggs, or in a dozen basketball nets. It impossible to answer this question. just like what is 1 + 1? 1 what + 1 what
http://answers.yahoo.com/question/index?qid=200609...

The unit of measure dozen refers simply to the number 12. Therefore, there are 12 two cent stamps in a dozen. Similarly, if one would ask, how many eggs are there in a dozen, then
http://www.webanswers.com/education/homeworkquest...

A dozen is a group of twelve. So there would be 12 stamps with a value of 36 cents. Thanks
http://www.chacha.com/question/howmanythreecent...
