# I don't understand what it means when they say write an expression with a variable. could you please write an example for me? Thank you.

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An *expression* can be thought of as just a bunch of mathematical symbols, put together in a way that makes sense according to the rules of mathematics. For example, the following are expressions:

*5 + 10*

*8 * (11 + 4) / 3 - 5*

*5^4*

As stated above, an expression must follow the rules of mathematics. For example, the following is NOT an expression: *4 *+--54(*

A *variable* can be thought of as something that holds the place of something else. Variables will commonly be denoted by the letters *x*, *y*.

An expression with a variable is just an expression that has a variable in it. The following are examples of expressions with variables:

*4x - 8y*

*8x^2 + 3x - 5*

*x / y*

Common textbook problems ask students to write an algebraic expression to resemble a verbal expression. For instance, "eight less than a number" translates to n-8. Algebraic expressions are a concise way to write lengthy verbal expressions. The following are a few more examples.

The sum of seven times a number and 3.

7x + 3

The product of two and the sum of a number and 9.

2(x + 9)

Twelve more than the quotient of a number and nine.

x/9 + 12

The quotient of a number and the sum of twelve and nine.

x/(12 + 9)

When writing an algebraic expression, make sure to read the verbal statement carefully. Most mistakes are caused by trying to get the problems done quickly.