SOLUTION: Please help me: A boy walked over hills at 3 kilometers per hour and on flat roads at 4 kilometers per hour. He walked 18 kilometers in 5 hours. How much of his trip was over hill

Question 139700: Please help me:
A boy walked over hills at 3 kilometers per hour and on flat roads at 4 kilometers per hour. He walked 18 kilometers in 5 hours. How much of his trip was over hills?
Thanks
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = km walked on hills
Let = km walked on flat groun

-------------------

Use substitution

Multiply each side by 12

km
6 km of the trip was over hills
check answer:

OK
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