87. Bus Ride. George went on a bus ride with his girlfriend, but after counting his limited resources, he realized they would have to walk back.

If the bus speed is 9 km/h, and the couple walks at 3 km/h, then how far can they ride so that the entire trip there and back takes 8 hours?
87. Young people travel three times faster by bus than on foot; therefore, \(\frac{3}{4}\) of the total time they need to spend on the return trip and only \(\frac{1}{4}\) of the time to travel by bus. Thus, they will travel for 2 hours, covering a distance of 18 km, and walk for 6 hours. They will return exactly 8 hours after departure.