# Chapter 9 - Basic Algebra - 9.8 Using Equations to Solve Application Problems - 9.8 Exercises - Page 689: 23

A variable is a letter that represents a number. Examples:: $x, y, \text{ and } z$ An expression is a sum, difference, product, or quotient of numbers and variables/letters. Examples: $2x, 5x-3y, \text{ and } \frac{9x}{5}+2$ An equation is a mathematical statements that says two expressions are equal to each other. Examples: $2x=4 \\3x-5y=8 \\x^2-16=0$

#### Work Step by Step

A variable is a letter that represents a number. Examples of variables are: $x, y, \text{ and } z$ An expression is a sum, difference, product, or quotient of numbers and variables/letters. Examples are: $2x, 5x-3y, \text{ and } \frac{9x}{5}+2$ An equation is a mathematical statements that says two expressions are equal to each other. Examples are: $2x=4 \\3x-5y=8 \\x^2-16=0$

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