Yale University
Yale New Haven Teachers Institute: Solving Problems "By the Hundreds"
The Yale-New Haven Teachers Institute site contains various math exercises relating to percentage and consumer-related problems. An explanation of sales tax, a related problem and answer are given.
Help Algebra
Help algebra.com: Percents
Converting percents to and from decimals and fractions is demonstrated in detailed examples. Once the concept is understood, you can use it to solve equations that contain percents.