Answer:
20 students
Explanation:
Assuming the class is made entirely out of girls, if 16 girls do not have blond hair, they are 80% of the whole class (because 20% do have blond hair). If 80% of a class is 16 students, then 10% of the class is 2 students and 100% (the whole) class has 20 students.
Hope this helps :)