Points A, B, and C form a triangle. Complete the statements to prove that the sum of the interior angles of ΔABC is 180°.

Answer: ∠1 = ∠4 and ∠3 = ∠5  ( alternate interior angle).Step-by-step explanation:Given : Triangle ABC with angle  1, 2, 3.To find : Complete the statements to prove that the sum of the interior angles of ΔABC is 180°.Solution : We have given that triangle ABC with angle  1, 2, 3.Here, line DE and AC are parallel and BA is traversal line.∠1 = ∠4 ( alternate interior angle)∠3 = ∠5 ( alternate interior angle)∠4 + ∠2+ ∠5 = 180  ( angle formed on line)∠1 + ∠2 + ∠3 = 180.Therefore, ∠1 = ∠4 and ∠3 = ∠5  ( alternate interior angle).