Given: <2 = <4, m<2 = 110

Proof: m<3 = 70

<2 = <4, m<2 = 110 Given

m<2 = m<4 Definition of congruent angles

m<4 = 110 b._______

<3 and <4 are a linear pair Definition of a linear pair(shown in diagram)

<3 and <4 are supplementary Linear Pair postulate

m<3 + m<4 = 180 c.________

m<3 = 70 d._______

I know the answers are a. Transitive

b. Definition of supplementary angles

c. Subtraction property of equality

but why? explain please!!