question: Jennifer's dog has 8 puppies, 3 of which have spots. Brandon's dog has 12 puppies, 4 of which have spots. What percentage of all the puppies have spots?
answer: First find the total number of puppies: 8 puppies + 12 puppies = <<8+12=20>>20 puppies
  Then find the total number of puppies with spots: 3 puppies + 4 puppies = <<3+4=7>>7 puppies
  Then divide the number of spotted puppies by the total number of puppies and multiply by 100% to find the percentage of puppies with spots: 7 puppies / 20 puppies * 100% = 35%
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