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Hi
Let x represent how miles can the boat travel on 60 gallons of gas
Question Sets Up the Proportion
  | cross multiplying to solve for x
  | cross multiplying to solve for x
  15x = 60gal*66mi
    x = 60*66/15gal
    x = 264mi
CHECKING our Answer
  4 times the gas, four times the miles that can be driven!