Complete the paragraph

proof.
Given: ∠1 and ∠2 are
supplementary, and ∠2 and
∠3 are supplementary.
Prove: ∠1 ≅ ∠3
By definition of supplementary
angles, m∠1 + m∠2 = _____
(a) and m∠2 + m∠3 = _____
(b). Then, m∠1 + m∠2 = m∠2
+ m∠3 by the __________
Property (c). Subtract m∠2
from each side. You get m∠1
= ______ (d), or ∠1 ≅ _____
(e).

By definition of supplementary angles, m∠1 + m∠2 = 180 (a) and m∠2 + m∠3 = 180 (b). Then, m∠1 + m∠2 = m∠2 + m∠3 by the Transitive Property (c). Subtract m∠2 from each side. You get m∠1 = m∠3 (d), or ∠1 ≅ ∠3 (e).