Answer:
The answer is 75 and here's why.
Let's figure out the amount of remaining votes to prove this.
250 total votes - 150 votes for candidate a = 100 votes.
minus ↑ sign
Candidate B received 25% of the votes, so let's find 25% of 100
100 * 0.25 = 25 votes
Candidate B only got 25 votes (that's kinda sad, poor guy)
100 - 25 votes = the # of votes candidate C got
Candidate C got 75 votes!