Question

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Proof

Statment Reason
ABC is a triangle Given
DE ||AC Given
∠ A = ∠ABD- Alternate interior angles are congruent
∠ C = ∠CBE- Alternate interior angles are congruent
∠ABD + ∠B + ∠CBE = 180°- ?
∠A + ∠B + ∠C = 180°- Substitution

Fill in the missing reason in the proof

A)
Definition of straight angles

B)
Alternate Interior Angles are congruent

C)
Supplementary angles sum up to 180°

D)
Complementary Angles sum up to 180°

Answer 1

well if you notice all three angles lie on the same line

Answer 2

Statment Reason
----------------------------------------------------------------
ABC is a triangle Given
DE ||AC Given
∠ A =~ ∠ABD Alternate interior angles are congruent
∠ C =~ ∠CBE Alternate interior angles are congruent
∠ABD + ∠B + ∠CBE = 180°
∠A + ∠B + ∠C = 180° Substitution

Answer 3

I don't see how this can be done in only one step.

Answer 4

yeah these questions are questionable

Answer 5

My guess is the answer they are looking for is A., but I don't agree with it.

Answer 6

hmm i thought maybe C??

Answer 7

wait never mind

Answer 8

It could also be that, but like I stated above, I don't agree with the way this problem is given.
The definition of supplementary angles is TWO angles whose measures add to 180 deg.
Here you have 3 angles, not 2. That's why in my opinion, this needs to be done in more than one step.