Solve the problems that contain variables:
http://www.math10.com/en/math-games/games/equalities/games-equation-with-one-variable.html
http://www.aaamath.com/equ723-evaluate-1variable.html#section3
http://www.quia.com/rr/42586.html
Algebraic Expressions:
http://www.math-play.com/Algebraic-Expressions-Millionaire/algebraic-expressions-millionaire.html
Solve Story Problem using Variables:
http://www.softschools.com/quizzes/math/expressions_and_variables/quiz815.html