question: Will buys 15 oranges. When he gets home, he asks his 2 sons to wash as many oranges as they are years old. The oldest son is 8 years old, the youngest is half as old as the oldest. How many oranges are left unwashed?
answer: The older son washes 8 oranges, so the younger son washes 8 / 2 = <<8/2=4>>4 oranges.
  Together they wash 8 oranges + 4 oranges =<<8+4=12>>12 oranges
  There are 15 oranges - 12 oranges = <<15-12=3>>3 oranges left unwashed.
  #### 3