Not really sure about what kind of an answer you want here...
I think you should count up every student's favorite choice and create a table. Then, let's just say there are a total of 30 students. 25 prefer ice cream over cake. The fraction of the students who prefer ice cream over cake is [tex]\frac{25}{30} = \frac{5}{6}[/tex].
Using a calculator, divide 5/6 to find the decimal percentage. 5/6 = 0.8333 (continuing on forever). Fractions are always more accurate, so when finding the percentage it won't be fully accurate since the 3s continue forever. This will be with a lot of numbers like 1/3 or even 2/3.
Now, shift the decimal two spaces forward, making 83.33
83.33% is your answer to this example problem I have created.
Do the same with yours!
Hope this helped! Feel free to ask anything else.