Rocio leaves point a traveling due east at 40 miles per hour. at the same moment, li leaves point a traveling due west at 50 miles per hour. after how many hours will they be 405 miles apart? )

Their speed of separation will be equal to the sum of their speeds because they are in opposite directions.
Speed of separation = 40 + 50 = 90 miles per hour

Time = distance / speed
Time = 405 / 90
Time = 4.5 hours

The answer for this question is 80