A group of students went to the activity. Men wore white hats and women wore red hats. During the break, they sat together and found that each boy saw as much white as red hat, while each girl saw twice as much white as red. How many students are there?

Solution: Everyone can't see the color of the hat on their heads. There are x boys, and each boy sees as many white hats as red hats, so the number of boys looking at girls is (X- 1). That is, * * * has (X- 1) girls. Every girl sees twice as much white as red, so the number of boys each girl sees is

2. According to the number of boys, we can get X=2(X-2) and X=4.

That is four boys, three girls and seven people.