Answer:
a) 13%
b) 45%
c) 16%
Explanation:
To calculate what percentage is one number (a) of another (b), you have to divide a by b and then multiply result by 100. In this case number of students with grade A is 4, total number of students is 31, therefore 4/31 * 100 = 12.9%. Rounding it to the nearest percentage will give you 13.
Just repeat the same steps for the remaning questions.