Answer:
1. linear pair
2. Substitution Property of Equality
3. Subtraction Property of Equality
4. <1 ≅ <3
Step-by-step explanation:
1. linear pair
A linear pair is a pair of angles that that are adjacent and add to 180 degrees
linear Pair Postulate states: "If two angles form a linear pair, then the angles are supplementary.
2. Substitution Property of Equality
<1 + <2 = 180 and <2+ <3 = 180
<1 + <2 = <2 + <3
3. Subtraction Property of Equality
<1 + <2 - <2= <2 - <2+ <3
<1 = <3
4. <1 ≅ <3
