Step-by-step explanation:
Given : ∠3 and ∠4 forms a linear pair
∠2 and ∠3 forms a linear pair
Two angles that forms a linear pair at supplementary. 'the linear pair postulate'
Sum of two angles of linear pair = 180 degree
∠3 + ∠4 = 180 linear pair postulate
Also ∠2 + ∠3 = 180 because it is a linear pair
Now substitute ∠2 + ∠3 for 180 in the above equation
∠2 + ∠3 = ∠3 + ∠4 Substitution property of equality
Cancel out angle 3 on both sides
so ∠4 = ∠2 Substitution property of equality
