13.054. One farmer obtained an average buckwheat yield of 21 tons per hectare, while another, who had 12 hectares less under buckwheat, achieved an average yield of 25 tons per hectare. As a result, the second farmer collected 300 tons more buckwheat than the first. How many tons of buckwheat were collected by each farmer?
Solution.

Let's compile the following table:

| Farmer | Area, ha | Yield, c/ha | Mass, c |
| :---: | :---: | :---: | :---: |
| First | $x$ | 21 | $21 x$ |
| Second | $x-12$ | 25 | $25(x-12)$ |

According to the condition $25(x-12)-21 x=300$, from which $x=150$. Then $21 x=3150$ (c); $25(x-12)=3450$ c.

Answer: 3150 and 3450 c.