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/2011/11/02/test-yourself-math-nov-2-2011-2/

This article is about the $18 million reportedly earned by Kim Kardashian and Kris Humphries as a result of their 72-day marriage.

How many years would an average person have to work in order to earn that much?