3.6 One farmer obtained an average buckwheat yield of 21 centners per 1 hectare, while another, who had 12 hectares less under buckwheat, achieved an average yield of 25 centners per 1 hectare. As a result, the second farmer collected 300 centners more buckwheat than the first. How many centners of buckwheat were collected by each farmer?
3.6 Let's compile the following table:

| Farmer | Area, ha | Yield, units/ha | Mass, centners |
| :---: | :---: | :---: | :---: |
| 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 $21 x=3150$ (centners), and $25(x-12)=3450$ (centners).