We have the frequencies for each of the grades. We can estimate the number of students graded by adding all those frequencies. Let's call N the total number of grades:
[tex]\begin{gathered} N=4+10+17+6+2 \\ N=39 \end{gathered}[/tex]We have then a total number of grades of 39.
The corresponding relative frequency for a grade is the ratio of the frequency to the total number of "samples", 39 in this case.
Then, for grade A, the relative frequency (RF) will be:
[tex]RF_A=\frac{4}{39}\approx0.10256\approx10.26\text{ \%}[/tex]This will be the fraction of the total grades that are A. Represented as a percentage will be 10.26%, rounded to two decimal places.
Now, to complete the table we do the same for the other frequencies:
For grade B:
[tex]RF_B=\frac{10}{39}\approx0.2564\approx25.64\text{ \%}[/tex]For grade C:
[tex]RF_C=\frac{17}{39}\approx0.4359\approx43.59\text{ \%}[/tex]For grade D:
[tex]RF_D=\frac{6}{39}\approx0.1538\approx15.38\text{ \%}[/tex]For grade F:
[tex]RF_D=\frac{2}{39}\approx0.0513\approx5.13\text{ \%}[/tex]