We can't have 24 10-year-olds in a class of 20,

nor can we have 6 girls if 16 are boys.

Can you double-check the question ?

Presumably there are 30 students in the class.

Then, if you arrange the situation as sets,

with x being the number of 10-year-old boys

30=16-x+x+24-x+6

30=46-x

Hence, all the boys would be 10 years old