a.) First check on the height of the bar that ranges between 20 and 24 which is 6. The 6 is the number of students who bought 20 books or more, so get the percentage of those students who bought 20 or more books; divide 6 which is the number of students who bought 20 books or more with the total number of students which is 40 then multiply with 100.
% of students who bought 20 or more books = 6/40 ×100
