The reason that justifies why Rachel stated that m∠4 + m∠5 + m∠6 = 180° is: A. Triangle sum theorem
What is the Triangle Sum Theorem?
The triangle sum theorem states that for any given triangle, the sum of all its interior angles will be equal to 180°.
Thus, given the diagram showing a triangle, where ∠4, ∠5, and ∠6 are supplementary angles to the interior angles ∠1, ∠2, and ∠3 of the triangle.
Since all interior angles add up to 180°, the sum of their supplements, ∠4, ∠5, and ∠6 will also be 180°.
Therefore, the reason that justifies why Rachel stated that m∠4 + m∠5 + m∠6 = 180° is: A. Triangle sum theorem
Learn more about triangle sum theorem on:
https://brainly.com/question/19805547
