Since the first car travels 55 miles per hour and starts an hour early, by 4:00 it is 55 miles away from the other car. Therefore, the equation is 55+a(some value)+b(another value)=380. If a car travels 55 miles per hour, that means that we add 55 for each hour and 55*x (if x is the number of hours) is the distance traveled. We have accounted for the first hour, so this is similar to saying that they start 55 miles away at 4:00 and go from there. For the other car, since it travels 75 miles per hour, its distance in hours is 75*x (the amount of time spent should be the same if we start at 4:00). Therefore, since they travel away from each other, our total distance is 55+55x+75x=380. Subtracting 55 from both sides (and combining like terms), we get 130x=325. Next, we divide both sides by 130 to get 2.5 hours, or 2 hours and 30 minutes
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