## Evaluating Variable Expressions with Integers

Contents

Now we’ll practice evaluating **expressions** that involve **subtracting negative numbers** as well as positive numbers.

## Example

Evaluate \(x-4\phantom{\rule{0.2em}{0ex}}\text{when}\phantom{\rule{0.2em}{0ex}}\)

- \(\phantom{\rule{0.2em}{0ex}}x=3\phantom{\rule{0.2em}{0ex}}\)
- \(\phantom{\rule{0.2em}{0ex}}x=-6.\)

### Solution

To evaluate \(x-4\) when \(x=3\), substitute \(3\) for \(x\) in the expression.

Subtract. |

To evaluate \(x-4\) when \(x=-6,\) substitute \(-6\) for \(x\) in the expression.

Subtract. |

## Example

Evaluate \(20-z\phantom{\rule{0.2em}{0ex}}\text{when}\phantom{\rule{0.2em}{0ex}}\)

- \(\phantom{\rule{0.2em}{0ex}}z=12\phantom{\rule{0.2em}{0ex}}\)
- \(\phantom{\rule{0.2em}{0ex}}z=-12\)

### Solution

To evaluate \(20-z\phantom{\rule{0.2em}{0ex}}\text{when}\phantom{\rule{0.2em}{0ex}}z=12,\) substitute \(12\) for \(z\) in the expression.

Subtract. |

To evaluate \(20-z\phantom{\rule{0.2em}{0ex}}\text{when}\phantom{\rule{0.2em}{0ex}}z=-12,\phantom{\rule{0.2em}{0ex}}\text{substitute}\phantom{\rule{0.2em}{0ex}}-12\phantom{\rule{0.2em}{0ex}}\text{for}\phantom{\rule{0.2em}{0ex}}z\phantom{\rule{0.2em}{0ex}}\text{in the expression.}\)

Subtract. |