Geometry: Proofs Addition and Subtraction Properties
Proving segments or angles are congruent using Addition or Subtraction Postulate.
If a segment or angle is added to congruent segments, then the sums are congruent
If a segment or angle is subtracted from congruent segments or angles, then their differences are congruent.
First things first look at the Givens and the Diagram and identify any postulates of theorems you see. Then see if you can elaborate on those facts. Continue adding rules and facts until you get to what needs to be proven. Sometimes that takes 2 or 3 steps then other times it can take a little bit more. That is what Proofs are all about, proving a fact is what you say it is...