Question

State which definition, postulate, or theorem justifies the statement about the diagram.

$m\angle 3+m\angle 4=180$

Short answer

The definition of a pair of Linear Angles justifies the statement about the diagram.

Step-by-step solution

Step 1. Observe the given diagram.

The diagram constitutes a triangle ABC.

Step 2. State the definition of a pair of linear angles.

When two lines intersect, two adjacent angles are formed. These adjacent angles are known as a linear pair and the sum of these two angles is 180.

Step 3. State the conclusion.

Considering the given diagram here $\angle 3$and $\angle 4$form a linear pair. So, the sum of these two angles is 180.

Therefore, the statement about the diagram is justified by the definition of a pair of linear angles.