Answer:
1) c ║ d by consecutive interior angles theorem
2) m∠3 + m∠6 = 180° by transitive property
3) ∠2 ≅ ∠5 by definition of congruency
4) t ║ v 
Corresponding angle theorem
5) ∠14 and ∠11 are supplementary Definition of supplementary angles
6) ∠8 and ∠9 are supplementary Consecutive interior angles theorem
Step-by-step explanation:
1) Statement Reason
m∠4 + m∠7 = 180° Given
m∠4 ≅ m∠6 Vertically opposite angles
m∠4 = m∠6 Definition of congruency
m∠6 + m∠7 = 180° Transitive property
m∠6 and m∠7 are supplementary Definition of supplementary angles
∴ c ║ d Consecutive interior angles theorem
2) Statement Reason
m∠3 = m∠8 Given
m∠8 + m∠6 = 180° Sum of angles on a straight line
∴ m∠3 + m∠6 = 180° Transitive property
3) Statement Reason
p ║ q Given
∠1 ≅ ∠5 Given
∠1 = ∠5 Definition of congruency
∠2 ≅ ∠1 Alternate interior angles theorem
∠2 = ∠1 Definition of congruency
∠2 = ∠5 Transitive property
∠2 ≅ ∠5 Definition of congruency.
4) Statement Reason
∠1 ≅ ∠5 Given
∠3 ≅ ∠4 Given
∠1 = ∠5 Definition of congruency
∠3 = ∠4 Definition of congruency
∠5 ≅ ∠4 Vertically opposite angles
∠5 = ∠4 Definition of congruency
∠5 = ∠3 Transitive property
∠1 = ∠3 Transitive property
∠1 ≅ ∠3 Definition of congruency.
t ║ v Corresponding angle theorem
5) Statement Reason
∠5 ≅ ∠16 Given
∠2 ≅ ∠4 Given
∠5 = ∠16 Definition of congruency
∠2 = ∠4 Definition of congruency
EF ║ GH Corresponding angle theorem
∠14 ≅ ∠16 Corresponding angles
∠14 = ∠16 Definition of congruency
∠5 = ∠14 Transitive property
∠5 + ∠11 = 180° Sum of angles on a straight line
∠14 + ∠11 = 180° Transitive property
∠14 and ∠11 are supplementary Definition of supplementary angles
6) Statement Reason
l ║ m Given
∠4 ≅ ∠7 Given
∠4 = ∠7 Definition of congruency
∠2 ≅ ∠7 Alternate angles
∠2 = ∠7 Definition of congruency
∠2 = ∠4 Transitive property
∠2 ≅ ∠4 Definition of congruency
∠2 and ∠4 are corresponding angles Definition
DA ║ EB Corresponding angle theorem
∠8 and ∠9 are consecutive interior angles Definition
∠8 and ∠9 are supplementary Consecutive interior angles theorem.
