Some mathematical expressions have one variable. Learn how to evaluate one variable expressions.

## Related Topics

- How to Translate Phrases into an Algebraic Statement
- How to Simplify Variable Expressions
- How to Simplify Polynomial Expressions
- How to Use the Distributive Property
- How to Evaluate Two Variables

## Step by step guide to evaluating one variable

- To evaluate one variable expression, find the variable and substitute a number for that variable.
- Perform arithmetic operations.

### Evaluating One Variable – Example 1:

Solve this expression when \( x=2\). \(18 \ – \ 2 \ x\)

**Solution:**

First substitute \(2\) for \(x\), then:

\(18 \ − \ 2 \ x=18 \ − \ 2(2)=18 \ − \ 4=14\)

### Evaluating One Variable – Example 2:

Solve this expression. \(5 \ – \ 2 \ x ,x=\ – \ 1\)

**Solution:**

First substitute \(- \ 1\) for \(x\), then:

\(5 \ − \ 2 \ x=5 \ − \ 2 \ (- \ 1)=5 \ + \ 2=7\)

### Evaluating One Variable – Example 3:

Solve this expression. \(12-2x ,x=-1\)

**Solution:**

First substitute \(-1\) for \(x\), then:

\( 12-2x=12-2(-1)=12+2=14\)

### Evaluating One Variable – Example 4:

Solve this expression. \( -8+5x ,x=3\)

**Solution:**

First substitute \(3\) for \(x\), then:

\( -8+5x=-8+5(3)=-8+15=7\)

## Exercises for Evaluating One Variable

### Simplify each algebraic expression.

- \(\color{blue}{9 – x , x = 3}\)
- \(\color{blue}{x + 2, x = 5}\)
- \(\color{blue}{3x + 7, x = 6}\)
- \(\color{blue}{(– 3) + \frac{x}{4} + 2x, x = 16}\)
- \(\color{blue}{(– 2) + \frac{x}{7}, x = 21}\)
- \(\color{blue}{(– \frac{14}{x}) – 9 + 4x, x = 2}\)

### Download Evaluating One Variable Expressions Worksheet

## Answers

- \(\color{blue}{6}\)
- \(\color{blue}{7}\)
- \(\color{blue}{25}\)
- \(\color{blue}{33}\)
- \(\color{blue}{1}\)
- \(\color{blue}{-8}\)