If the ratio is 3:1 what is the percentage?

The question seems to me be missing some details.

I agree with Don’t Memorize’s answer for an interpretation of the question. It may be that the question more fully spelled out would be something like:

“If the ratio of ‘YES’ to ‘NO’ is 3:1 what are the percentages?”

in which case the answer would be ##75%## ‘YES’ to ##25%## ‘NO’.