Two dogsled teams raced across a 400-mile course in Alaska. Team A finished the course in 4 fewer hours than team B. If team A’s average speed was 5 miles per hour greater than that of team B, what was team B’s average speed, in miles per hour? Choose the correct choice from the following answers
A) 12	B) 15	C) 18	D) 20	E) 25
Let v be team B's average speed.   Time = Distance/Rate and the time difference was 4 hours.   400/v - 400/(v+5)= 4   400v + 2000 - 400v = 4(v)(v+5)   500 = (v)(v+5)   (20)(25) = (v)(v+5)   v = 20 mph   The answer is 20.
<result>D</result>
Two dogsled teams raced across a 400-mile course in Alaska. Team A finished the course in 4 fewer hours than team B. If team A’s average speed was 5 miles per hour greater than that of team B, what was team B’s average speed, in miles per hour?