Answer:
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Explanation:
Statement Reason
Points A, B, and C form a triangle. Given
Let be a line passing through B and parallel to . Definition of parallel lines
∠3 ≅ ∠5 and ∠1 ≅ ∠4 Definition of corresponding angles in parallel lines
m∠1 = m∠4 and m∠3 = m∠5 Substitution of corresponding angles
m∠4 + m∠2 + m∠5 = 180° Angle addition and definition of a straight line
m∠1 + m∠2 + m∠3 = 180° Substitution.