question: Rory makes a cake that weighs 20 ounces. She cuts into 8 pieces. Rory and her mom each have a piece. How much does the remaining cake weigh?
answer: Each piece of Rory’s cake weighs 20 ounces / 8 pieces = <<20/8=2.5>>2.5 ounces.
  If Rory and her mom each have a slice, they will have eaten 2.5 ounces + 2.5 ounces = <<2.5+2.5=5>>5 ounces.
  The rest of the cake weighs 20 ounces – 5 ounces = <<20-5=15>>15 ounces.
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