Get more lessons like this at http://www.MathTutorDVD.com In this lesson, we will learn what a variable is and why they are important in Algebra. A variable is a placeholder for a numerical value. If we don't know what a number is in an equation, we use a variable to represent the number. Usually we then solve the equation to find out what the value of the variable is. Variables can use any letter of the alphabet. "t" is commonly use for time. "a" can be used for acceleration. "v" can be used for velocity. Generically, we usually use "x" for variables in algebra.