A **number line** can be used to add and subtract negative numbers.

What is ?

To add -4 and 5, draw the starting number on a number line and count to the **right** when **adding** numbers.

So,

What is ?

To subtract 2 from -2, start at -2 on a number line, and count to the **left** when **subtracting** numbers.

What is the difference in temperature between a desert at 40 °C and a mountain top at -2 °C?

, so the difference in temperature between the desert and the mountain top is 42 °C.

To subtract a negative number, count to the right. **Subtracting a negative number is like adding a positive number**.

What is ?

To subtract -2 from 4, start at number 4 on a number line, and count to the right. So, .

When two **signs** are written next to each other, the rules for adding and subtracting numbers are:

- two signs that are
**different**become a**negative**sign - two signs that are the
**same**become a**positive**sign

- Same signs give a positive:
- Same signs give a positive:
- Different signs give a negative:
- Different signs give a negative:

- Question
Calculate .

- Question
Calculate .