Question

∠1 and ∠2 are supplementary and m∠1 = m∠3. Which one of these statements will always be true?

Answer 1

@Vocaloid m∠2 = m∠3

Answer 2

only work with the information you are given

m∠1 = m∠3

means <1 and <3 are congruent

so you can replace "<1" with <3 in the original statement "∠1 and ∠2 are supplementary"