Question 593076
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?
**
let x=distance walked over hills
18-x=distance walked over flat roads
travel time=distance/speed
..
x/3+(18-x)/4=5
LCD:12
4x+54-3x=60
x=6 km
ans: 
distance walked over hills=6 km