13.392 A car left the airport for the city center at the same time a bus left the city center for the airport. When the first had traveled half the distance, the second had 19.2 km left to reach the end of the route, and when the second had traveled half the distance, the first had 12 km left to reach the end of the route. How many kilometers does the bus have left to travel after the car completes its route?
Solution. Let the speed of the car be $x$ times the speed of the bus, and $z$ be the distance between the airport and the city center. Then, according to the condition, we have:

$\left\{\begin{array}{l}\frac{z / 2}{z-19.2}=x, \\ \frac{z-12}{z / 2}=x\end{array} \Leftrightarrow\left\{\begin{array}{l}z=32, \\ x=\frac{4}{5} .\end{array}\right.\right.$

Therefore, if the car travels the entire distance, the bus will travel $\frac{4}{5} \cdot 32$ km in the same time, i.e., it will have 6.4 km left to travel.

Answer: 6.4 km.