


Use simple problems like this to learn to solve problems. Complex problem are a collection of simple problems. All problem solutions have the solution structure shown here. The words change, the symbols change, the concepts change and the numbers change. The problem solving process does not change!
Once you have learned how to solve one problem, you have learned how to solve all problems. Learn how to solve problems! 
The problem is one of the Brain Teasers provided by Kaplan Education Centers. The site provides access to extensive information and resources on a variety of standard evaluation tests (SAT, GRE, MCAT etc) as well as other educational resources. This is a valuable educational site. 