Answer: Each team must have 9 runners if each runs 2/3 of a mile and the total distance is 6 miles
Explanation: The first runner goes 2/3, the second makes it 4/3, the third makes it 6/3, the fourth makes it 8/3, the fifth makes it 10/3, the sixth makes it 12/3, the seventh makes it 14/3, the eighth makes it 16/3 and the ninth runner makes it 18/3 which equals 6