As the final SparkNote within Pre-Algebra, this guide serves as the jumping off point from pre-algebra to algebra. As such, this chapter will introduce the reader to variables and how to evaluate expressions and solve equations that contain variables.

The first section will explain what a variable is and how variables are used. This is essential knowledge--variables are the crux of algebra.

The second section will deal with algebraic expressions--that is, expressions containing a variable. It will explain how to evaluate an algebraic expression, given a quantity for the variable.

The final section is an introduction to solving algebraic equations--equations that contain a variable. It will teach the reader how to determine which number a variable represents by using inverse operations. This topic will reappear in algebra; in fact, much of algebra is concerned with solving equations for variables.

The material covered in this section is very important. It is the gateway from pre-algebra to algebra. Much of this study guide has been concerned with understanding operations and how they can be applied to given numbers. Now, we will begin to explore operations on unknown numbers. This chapter will introduce the concept of representing unknown numbers by variables, which will be used in all of mathematics--algebra and beyond--as well as physics, chemistry, statistics, and economics.