13.026. A tourist traveled 90 km by boat along the river and walked 10 km on foot. For the walking route, 4 hours less were spent compared to the river journey. If the tourist had walked for as long as he had rowed, and rowed for as long as he had walked, these distances would have been equal. How long did he walk and how long did he row?
## Solution.

Let $x$ be the number of hours the tourist walked. Then he spent $(x+4)$ hours on the boat. The tourist's walking speed is $\frac{10}{x}$ km/h; the speed on the boat is $-\frac{90}{x+4}$ km/h. According to the problem, $\frac{10}{x}(x+4)=\frac{90}{x+4} \cdot x$, from which $x=2$ hours.

Answer: 2 and 6 hours.