13.118. Two buses left the factory simultaneously and headed to the recreation area, to the lake. The distance between the factory and the lake is 48 km. The first bus arrived at the lake 10 minutes earlier than the second, and the average speed of the second bus is 4 km/h less than the average speed of the first. Calculate the speeds of the buses.
## Solution.

Let $x$ km/h be the speed of the first bus, and $x-4$ km/h be the speed of the second bus. The first bus arrived at the lake in $\frac{48}{x}$ hours, and the second bus in $\frac{48}{x-4}$ hours. According to the condition, $\frac{48}{x-4}-\frac{48}{x}=\frac{1}{6}$, from which $x=36$ km/h, $36-4=32$ km/h.

Answer: 32 and 36 km/h.