Math-a-mystery!

Today I solved a weird and hard math open response. We had to show our working process and that was the thing that counts most. I was almost the one that got it and it quite made sense to me when I focused hard. I will tell you the math problem. Mr.Morris's class is making dolls for the school fair. They are called buton dolls because their eyes are made of buttons and the doll's clothes always has 3 buttons. The buttons are sold in 12 pieces per package. Mr. Morris wants to have no leftovers. How many packages does he have to buy? How many dolls are made?