Question: Daniela began a plan for this proof. Since ∠1 and ∠2 are supplementary and ∠2 and ∠3 are supplementary, then m∠1+m∠2=180° and m∠2+m∠3=180°. If she can get m∠1 and m∠3 to both equal the same expression, she can use the transitive property of equality to set them equal to each other. How can Daniela get m∠1 and m∠3 to both equal the same expression?

Answer: She can subtract m∠2 from both sides of m∠1+m∠2=180° and m∠2+m∠3=180°