What the given proof is trying to show us is that; ∠3 = 126°
How to prove supplementary angles?
From the attached line, we see that angle 1 and angle 3 form a straight line. Now, since we know that angles on a straight line sum up to 180°, then it means that they are supplementary.
We are given;
1) ∠1 and ∠2 are supplementary
2) ∠1 = 36°
Thus from definition of complementary angles, we can say that;
36° + ∠2 = 90°
Subtraction property of equality when applied gives;
∠2 = 54°
We are told that ∠2 and ∠3 are linear pairs and as such;
∠2 + ∠3 = 180° from linear pairs theorem.
By substitution property of equality we have;
54° + ∠3 = 180°
Solving gives ∠3 = 126°
Read more about Supplementary Angles at; https://brainly.com/question/2046046
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