8.1. A dandelion blooms in the morning, remains yellow for this and the next day, turns white on the third morning, and by evening of the third day, it has lost its petals. Yesterday afternoon, there were 20 yellow and 14 white dandelions on the meadow, and today there are 15 yellow and 11 white. How many yellow dandelions were there on the meadow the day before yesterday? Provide all possible answers and prove that there are no others.
Solution: All yellow dandelions the day before yesterday are the white dandelions of yesterday and the white dandelions of today. Therefore, the day before yesterday there were $14+11=25$ yellow dandelions.

Answer: 25 dandelions.

Note: The number of yellow dandelions yesterday and today is not needed for solving the problem.

Recommendations for checking:

| is in the work | points |
| :--- | :--- |
| Correct justified answer | 7 points |
| Answer without justification OR incorrect answer | 0 points |