# Angles On One Side of A Straight Line

Angles on one side of a straight line always add to **180 degrees**

30° + 150° = **180° **

When a line is split into 2 and we know one angle, we can always find the other one.

### Example: We know one angle is 45°, what is the other angle **"a"** ?

Angle a is 180° − 45° =
135° |

This method can be used for several angles on one side of a straight line.

### Example: What is angle **"b"** ?

Angle Sum of known angles = 45° + 39° + 24°
Angle |