15. The teachers and students of a township primary school went to the county town for a visit. It was stipulated that the bus would depart from the county town and arrive at the school at 7:00 AM to pick up the visiting teachers and students and immediately head to the county town. However, the bus broke down on its way to the school and had to stop for repairs. The teachers and students at the school waited until 7:10 AM but still did not see the bus, so they started walking towards the county town. On their way, they met the repaired bus, immediately got on, and headed to the county town, arriving 30 minutes later than the originally scheduled time. If the speed of the bus is 6 times the walking speed, how long did the bus spend on the road for repairs?
15. Suppose it took \( x \) minutes to fix the car. As shown in Figure 8, let point \( A \) be the location of the county town, point \( C \) be the location of the school, and point \( B \) be the place where the teachers and students met the car on the way.

In the 30 minutes that the teachers and students were late to the county town, 10 minutes were due to the late departure, and another 20 minutes were due to walking from \( C \) to \( B \) instead of taking the car.

The 30 minutes that the car was late were partly due to the \( x \) minutes spent fixing the car, and partly due to the time saved by not making a round trip between \( B \) and \( C \).

Given that the car's speed is 6 times the walking speed, and that walking from \( C \) to \( B \) takes 20 minutes longer than taking the car, it follows that the car should take \(\frac{20}{6-1}=4\) minutes to travel from \( C \) to \( B \). A round trip saves 8 minutes.
Therefore, \( x - 8 = 30 \), so \( x = 38 \).
That is, it took 38 minutes to fix the car on the way.