What do supplementary angles sum to?

Supplementary angles are defined as two angles whose measures add up to 180 degrees. This term is essential in geometry, particularly when dealing with the properties of angles formed by parallel lines and transversals, as well as in various geometric shapes. The concept of supplementary angles is crucial in solving many geometric problems, as it helps in determining unknown angles and in understanding angle relationships better.

While it's easy to confuse the properties of different types of angles, knowing that supplementary angles specifically sum to 180 degrees is a foundational aspect of angle relationships in geometry. This is why the correct answer reflects that property of supplementary angles.