If you have a gross of items, you have 144 items. If you buy a gross of eggs, how many dozen eggs do you have?

This is a simple division problem. If you think about it, it says that on gross of items is 144 items. In this case we are talking about eggs. You should know that there is 12 items (eggs) in a dozen. Therefor,

144 / 12 = 12.

"1 gross" means 1 dozen dozens.