25/50 * 100% is the expression that gives the percent of voters who voted from candidate b.
Candidate B. 25/50 = 0.50 * 100% = 50%
Candidate A. 15/50 = 0.30 * 100% = 30%
Did not vote (50-25-15)/50 = 10/50 = 0.20 * 100% = 20%
Voted Candidate A 15 30%
Voted Candidate B 25 50%
Did not vote 10 20%
Total number of students 50 100%