2010 AMC 10B Problems/Problem 12

The minimum possible value occurs when 20% of the students who originally answered "No." answer "Yes." In this case, x=20

The maximum possible value occurs when 30% of the students who originally answered "Yes." answer "No." and the 50% of the students who originally answered "No." answer "Yes." In this case, x=50+30=80

Subtract 20 from 80 to obtain an answer of