Peter went upstream in a canoe at an average speed of 12 miles per hour. he returned by the same route at an average speed of 18 miles per hour. what was peter's average speed for the round trip, in miles per hour?

Which labels do x and y represent? x: scattered bundles y: multiples of four or five x: scattered bundles y: multiples of three x: bundles in a ring y: multiples of four or five x: bundles in a ring y: multiples of three