Problem 1. In a multicolored family, there were an equal number of white, blue, and striped octopus children. When some blue octopus children became striped, the father decided to count the children. There were 10 blue and white children in total, while white and striped children together amounted to 18. How many children are there in the multicolored family?
Answer: 21.

First solution. Note that the white octopuses were one third of the total number, and they did not change color. If we add 10 and 18, we get the total number of all children, plus the number of white ones, which is $4 / 3$ of the total number of all children. Thus, $4 / 3$ of the number of children in the family is 28, which means there are 21 children in total.

Second solution. After recoloring, the number of striped octopuses became $18-10=8$ more than the blue ones. This means that $8: 2=4$ blue octopuses turned striped. There were $18-4=14$ white and "old striped" octopuses, which means there were $14: 2=7$ of each color. Therefore, there are $3 \cdot 7=21$ children in the colorful family.