The question asks about the sum of angles that form a linear pair.

A linear pair of angles occurs when two adjacent angles are formed by two intersecting lines. These angles are supplementary, meaning their measures add up to 180°.

Thus, the correct answer for the green box is:

$180^\circ$

Would you like further details on linear pairs or related concepts?

Here are 5 related questions you might find helpful:

1. What are supplementary angles, and how are they different from complementary angles?
2. How do you identify linear pairs in different types of geometric figures?
3. Can angles forming a linear pair ever be equal? If so, under what conditions?
4. How do linear pairs relate to the concept of vertical angles?
5. What is the significance of linear pairs in real-life applications?

Tip: When solving geometry problems, always remember that linear pairs are supplementary, which simplifies angle calculations in many scenarios!