5. Two tribes share one shaman. One tribe lives in the river valley, the other - on a hill, on the slope of a mountain. Due to the spread of the internet and rumors, the shaman had to lower the prices for his services. For the tribe living in the valley, the price "in furs" was reduced by $10 \%$ and "in fish" by $15 \%$. The ratio of the prices of furs and fish in the local market is constant. For the tribe on the hill, the price "in furs" was reduced by $20 \%$. By how many percent did the price of services "in fish" decrease for this tribe? Round the answer to one decimal place.
Solution. For the tribe living in the valley, the price reduction in "furs" is $0.9 x$; in "fish" it is $0.85 x$. The price ratio in the local market is constant $\frac{0.9}{0.85}=\frac{18}{17}$. For the tribe on the hill, the reduction in "furs" is $0.8 x$, and let the price in "fish" be $y$. $\frac{18}{17}=\frac{0.8 x}{y} ; y=\frac{0.4 x \cdot 17}{9} ;\left(1-\frac{6.8}{9}\right) x=\frac{2.2 x}{9}$; the reduction in percentage is $\frac{2.2 x}{9 x} \cdot 100 \%=\frac{220}{9}=24.4$

## Answer: $24.4$.