Answer: 70%
Step-by-step explanation:
Not sure if this is correct but according to the red numbers there is a total of 20 classes. Looking at how many of these classes have 21 or more students we can see that the last three bars contain classes of 21 or more students. The last three bars contain a total of 14 of the 20 classes.
14/20 = 0.7 = 70%
meaning 70% of the classes contain at least 21 students.
