Aclass of 33 students elected a class treasurer. there were 11 votes for candidate a and 15 votes for candidate b. the rest of the class did not vote. which expression gives the percent of voters who voted for candidate a?

Well there's no expressions to list, but:
First you have 33 students, 11 voted for Candidate A, 15 voted for Candidate B, the remaining 7 didn't vote for either.
We're looking for the percentage for Candidate A, being: 11/33 which can be reduced down to 1/3rds, 1/3rds is equivalent to 0.333... which in reference if multiplied by 100 gives you 33.3% (estimated).

So your answer should be that 33.3% of the class voted for Candidate A.

Hope that helps. ^ ^
{-Ghostgate-}

20 percentage, you can also do it on a calculator.