I encountered this question before. The correct phrasing of this question was:
Last night, 80 people attended a lecture at the Smithville Public Library. 47 of the attendees were men. What ratio BEST represents the relationship between the number of men and the number of women?
Given:
80 people
47 were men
80-47 = 33 number of women.
Number of men : 47
Number of women : 33
Ratio that best represents the relationship between the number of men and the number of women is 47 : 33.