Substitution

SAS (Side-Angle-Side)

DB = EB

Algebra

AB = DA + DB and CB = EC + EB

Reflexive

Substitution

<A = <C

AE = CD

Triangle DBC = Triangle EBA

Triangle DAC = Triangle ECA

DA + DB = EC + EB

CPCTC

Reflexive

CPCTC

SSS (Side-Side-Side)

AB = CB, DA = EC

CB = DA + DB

EC + DB = EC + EB

<B = <B

AC = AC

Given

Segment addition theorem

Substitution