Math Quiz: NYT Learning Network

Through Math for America, I am part of an on-going collaboration with the New York Times Learning Network.  My latest contribution, a Test Yourself quiz-question, can be found here:

https://learning.blogs.nytimes.com/2012/01/25/test-yourself-math-jan-25-2012/

This question is based on the rising number of weight-loss surgeries performed each year in the U.S.  How many are being performed on patients under 21 years of age?