Half of the children in 5.A attend a dance club. All girls attend and one third of the 18 boys attend.

a) How many children are in 5.A?

b) How many girls are in 5.A?
All girls and one third of 18 boys, i.e., 6 boys, attend the dance club, which is half of the students in 5.A. 12 boys, who do not attend the dance club, make up the other half of the class.
a) There are thus 24 children in class $V$.
b) $24-18=6$. There are 6 girls.

[ 6 boys ... 1 point, 12 boys are half ... 1 point, 24 children in the class ... 2 points, 6 girls ... 2 points]