question: Jay is making snowballs to prepare for a snowball fight with his sister. He can build 20 snowballs in an hour, but 2 melt every 15 minutes. How long will it take before he has 60 snowballs?
answer: Every hour, Jay makes 20 snowballs.
  At the same time, each hour 2 * 60/15 = <<2*60/15=8>>8 snowballs melt.
  This means that each hour, Jay ends up with 20 – 8 = <<20-8=12>>12 more snowballs.
  It will take Jay 60 / 12 = <<60/12=5>>5 hours to create enough snowballs.
  #### 5