Given: m∠4 = m∠2
m∠5 = m∠3
m∠DBE = 180∘

Prove: m∠1 + m∠2 + m∠3 = 180∘

Match each numbered statement in the proof to its correct reason.

1. m∠4=m∠2
m∠5=m∠3
m∠DBE=180∘

2. m∠4+m∠1+m∠5=m∠DBE

3. Because m∠DBE=180∘,
m∠4+m∠1+m∠5=180∘.

4. Because m∠4=m∠2 and m∠5=m∠3,
m∠2+m∠1+m∠3=180∘.

5. m∠1+m∠2+m∠3=180∘

Given
Angle Addition Postulate
Transition Property of Equality
Substitution Property of equality
commutative Property of Addition