Wade Ellis and Denny Burzynski's "Basic Properties of Real Numbers: Properties of the Real Numbers"

Read this section through "Sample Set A," and work through the exercises in Practice Set A. The solutions to the practice problems are shown directly below each problem.

You know that changing the order in which two numbers are added does not change the result, and, likewise, changing the order in which two numbers are multiplied does not change the result. Because variables represent numbers, this is true for variables as well. With the help of this reading, you will learn to apply this property to any expression.