7 students out of 58 have no opinion, so probability=7/58=12.07%.
Probability of being a freshman is 28/58 and probability of a random student answering no is 7/58, so the chances of one or the other is 28/58+7/58=35/58=60.34%.
24/58=41.38% is the probability of a sophomore favouring the issue.
Since a non-freshman means a sophomore and not favouring the issue means no or no opinion, the probability is 6/58=10.34%.