13.036. Fresh mushrooms contain $90 \%$ water by mass, and dried mushrooms contain $12 \%$. How many kilograms of dried mushrooms can be obtained from 22 kg of fresh mushrooms?
## Solution.

Let $x$ kg of dried mushrooms be obtained from 22 kg of fresh mushrooms. Then the water in the dried mushrooms is $0.12 x$. According to the condition, $x - 0.12 x = 22(1 - 0.9); 0.88 x = 2.2$. Hence, $x = 2.5$ kg.

Answer: 2.5 kg.