question: John invited 20 people to a birthday party.  Each guest will eat 2 hot dogs.  He already has 4 hot dogs left over from a previous party.  If a pack of hot dogs contains 6 hot dogs and costs $2, how much does he need to spend on hot dogs?
answer: He needs 2*20=<<2*20=40>>40 hot dogs
  So he needs another 40-4=<<40-4=36>>36 hot dogs
  So he needs to buy 36/6=<<36/6=6>>6 packs of hotdogs
  That means he needs to spend 6*2=$<<6*2=12>>12
  #### 12