To fill in the frequencies, we will need to count the numbers of students having a certain grade
For example for the A grade, we count the number of students having this
After doing this, we put in the number in the frequency tab
In cases where no student had a particular grade, we put in zero
After filling all these frequencies, we proceed to get the cumulative frequency
Kindly note that the total frequency if properly done should be 25
Now, let us say we had 5 as the number of students with A, 6 as the number of students with A- and 1 as the number of students with B+
The cumulative frequency at A will be 6, the cumulative frequency at A- will be (5 + 6) = 11
The cumulative frequency at B+ will be 11 + 1 = 12