Task 1 - 200521 Two siblings received a total of 6 marks for recycling materials in September. In October, they received 13 marks together. In November, they got 2 marks less than the total of the two previous months.

A third of their total earnings over the three months was donated to solidarity, another third of the total earnings was put into their joint vacation fund. The rest was divided equally between them for personal use.

Determine the amount that each of the two received for their personal use!
Due to $6+13=19$ and $19-2=17$, the siblings received 17 marks together in November, and because $6+13+17=36$, they received a total of 36 marks.

Due to $36: 3=12$, their solidarity donation amounted to 12 marks. They put the same amount into their vacation fund.

Due to 36 - 12 - $12=12$, 12 marks remained, of which each received half, so each received 6 marks.