Algebra
posted by Rose .
A carload of fraternity brothers leaves their house for a long weekend road trip. Two hours later a second carload of brothers leaves the same house and travels the same path. If the second car drives an average of 15 mph faster than the first, what is the average speed of each car if it takes the second car four hours to catch up to the first?

we have two cars, Slow and Fast.
f travels 4 hours at a speed of s+15
distance = speed * time
s*6 = (s+15)*4
6s = 4s + 60
2s = 60
s = 30
So,
s goes 30mph for 6 hours = 180 miles
f goes 45mph for 4 hours = 180 miles