# Basic Algebra/Introduction to Basic Algebra Ideas/Variables and Expressions

## Vocabulary[edit]

- Variable
- Term
- Operation
- Expression
- Evaluate
- Substitute

## Lesson[edit]

A **variable** is a letter or symbol that takes place of a number in Algebra. Common symbols used are , , , and . The letters **x** and **y** are commonly used, but remember that any other symbols would work just as well.

Variables are used in algebra as placeholders for unknown numbers. If you see **"3 + x"**, don't panic! All this means is that we are adding a number who's value we don't yet know.

Some examples of variables in use:

- -- three times of .
- -- five minus
- or -- 2 divided by

A **term** is a number or a variable or a cluster of numbers and variables multiplied and or divided separated by addition and subtraction.

**Examples of terms:**

- The terms are 3 and 5.
- The term is , 6 over is one term, because the operation is division.
- The terms are 6 and 5, 6 and 5 are separate terms because they are separated by a addition or subtraction.

An **operation** is a thing you do to numbers, like add, subtract, multiply, or divide. You use signs like **+**, **–**, *****, or **/** for operations.

An **expression** is two or more terms, with operations between all terms.

**Examples of expressions:**

To **evaluate** an expression, you do the operations to the terms of an expression.

**Examples of evaluating expressions:**

- evaluates to
**7**. - evaluates to
**6**. - evaluates to
**17**.

To evaluate an expression with variables, you **substitute** (put a thing in the place of an other thing) numbers for the variables.

**Examples of substituting:** (Substitute 3 for x in these examples.)

- is .
- is .
- is .

## Example Problems[edit]

**Evaluate when is 2.**

Substitute 2 for to get .

Evaluate to get the answer 10.

**Evaluate when is 9 and is 4.**

Substitute 9 for and substitute 4 for is to get .

Evaluate to get the answer 7.

## Practice Games[edit]

## Practice Problems[edit]

remember order of operations