Question

given: $overleftrightarrow{bc}$ is parallel to $overleftrightarrow{ed}$
$mangle abc = 70^circ$
$mangle ced = 30^circ$
prove: $mangle bec = 40^circ$

statement	justification
$mangle abc = 70^circ$	given
$mangle ced = 30^circ$	given
$mangle abc = mangle bed$	corresponding angles theorem
$mangle bec + mangle ced = mangle bed$	angle addition postulate
$mangle bec = 40^circ$	subtraction property of equality

which of the following accurately completes the missing statement and justification of the two - column proof?
$mangle bec + 30^circ = 70^circ$ substitution property of equality

Explanation:

Step1: Substitute known angle values

$m\angle BEC + 30^\circ = 70^\circ$

Step2: Apply substitution property

Justification: Substitution Property of Equality

Answer:

Missing Statement: $\boldsymbol{m\angle BEC + 30^\circ = 70^\circ}$
Missing Justification: $\boldsymbol{\text{Substitution Property of Equality}}$