Explanation:
Statement . . . . Reason
1. ∠1 and ∠2 are a linear pair; ∠2 and ∠4 are a linear pair . . . . given
2. ∠1+∠2 = 180°, ∠2+∠4 = 180° . . . . definition of linear pair
3. ∠1+∠2 = ∠4+∠2 . . . . substitution property of equality
4. ∠1 = ∠4 . . . . subtraction property of equality
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In words: angles supplementary to the same angle are congruent.
