13.015. A tourist traveled the distance between two cities in 3 days. On the first day, he traveled $1 / 5$ of the total distance and an additional 60 km, on the second day $1 / 4$ of the total distance and an additional 20 km, and on the third day $23 / 80$ of the total distance and the remaining 25 km. Find the distance between the cities.
Solution.

Let $x$ km be the distance between the cities. We can form the following table:

| Day | Distance traveled in a day |
| :---: | :---: |
| First | $\frac{1}{5} x+60$ (km) |
| Second | $\frac{1}{4} x+20$ (km) |
| Third | $\frac{23}{80} x+25$ (km) |

According to the condition, $\frac{1}{5} x+60+\frac{1}{4} x+20+\frac{23}{80} x+25=x$, from which $x=400$.

Answer: 400 km.