# What is a Variable Expression? - Definition & Example Video

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• 0:00 Carbs & Runs
• 1:25 More for Maxwell
• 2:13 A Variety of Expressions
• 2:40 Equations & Expressions
• 3:07 Lesson Summary
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Lesson Transcript
Instructor: Joseph Vigil
In this lesson, we'll review variables before learning about variable expressions and viewing some examples. You can also test your knowledge with a brief quiz.

## Carbs & Runs

Sue runs a successful bakery and clears \$1,500 in profit every day. However, she's pledged \$100 to her friend Maxwell, who's participating in a run-a-thon to promote sugary carbs. Sue wants to know how much profit she'll have left after a given number of days.

Since Sue isn't working with a set number of days, she'll need to use a variable. A variable is a symbol that stands in for an unknown value. Any symbol can be used to represent a variable, so let's use the letter d for days. To find Sue's profit before the pledge, we would multiply her daily profit by the number of days she's working: 1,500 * d, which we can also write as: 1,500d. This is known as a term, which can be either a number, a variable, or a number and a variable multiplied together.

Now we need to take into account the deduction for Sue's pledge, so we would subtract \$100: 1,500d - 100. So, if d stands for the number of days Sue's working, her profit would be 1,500d - 100. Since the number 100 is another term, we've just created a variable expression, which is a combination of terms and mathematical operations that contains at least one variable.

In fact, we could string together any combination of variable terms and operations, and we would have a variable expression. As we've demonstrated above, they're handy in expressing situations with unknown values.

## More for Maxwell

All of Maxwell's friends have pledged \$100 for his run-a-thon. His father was so impressed with his work, he promised to pledge \$500 just before the run.

For Maxwell to determine his total pledge amount, he'll need to multiply 100 by the number of friends that pledged. While we used the letter d earlier, we can use any letter to represent a variable. We'll use the variable x here. So, the amount his friends pledged would be: 100 * x, or 100x.

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