question: A farm has 10 2-legged animals and 15 4-legged animals. If all animals are healthy, how many pairs of animal legs in total are on the farm?
answer: 2-legged animals have 2 legs. Therefore 10 2-legged animals will have 10*2=<<10*2=20>>20 legs
  4-legged animals have 4 legs. Therefore 15 4-legged animals will have 15*4=<<15*4=60>>60 legs
  In total there are 20+60= <<20+60=80>>80 legs
  A pair of legs equals 2 legs. If there are 80 legs on the farm, there will be 80/2= <<80/2=40>>40 pairs of legs
  #### 40