SOLUTION: During a trip of 385 miles, Fred averaged 15 miles per hour in the cities and 70 miles per hour on the highways. If the trip took a total of 7 hours, how much time did Fred spend d

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Question 1187022: During a trip of 385 miles, Fred averaged 15 miles per hour in the cities and 70 miles per hour on the highways. If the trip took a total of 7 hours, how much time did Fred spend driving in the cities?
Answer by josgarithmetic(39629) About Me  (Show Source):
You can put this solution on YOUR website!
                  SPEED            TIME         DISTANCE

Cities            15                x          15x

Highways          70              7-x          70(7-x)

totals                            7               385

Total distance is equation in one variable.
15x%2B70%287-x%29=385
Solve this.