Sometimes we use positive and negative numbers to represent quantities in context. Here are some contexts we have studied that can be represented with positive and negative numbers:

- temperature
- elevation
- inventory
- an account balance
- electricity flowing in and flowing out

In these situations, using positive and negative numbers, and operations on positive and negative numbers, helps us understand and analyze them. To solve problems in these situations, we just have to understand what it means when the quantity is positive, when it is negative, and what it means to add and subtract them.

When two points in the coordinate plane lie on a horizontal line, you can find the distance between them by subtracting their $x$-coordinates.

When two points in the coordinate plane lie on a horizontal line, you can find the distance between them by subtracting their $y$-coordinates.

Remember: the *distance* between two numbers is independent of the order, but the *difference* depends on the order.