In the figure, a//b , and both lines are intersected by transversal t. Complete

In the figure, a//b , and both lines are intersected by transversal t. Complete the statements to prove that ∠2 and ∠8 are supplementary angles.
(given)
m∠2 = m∠7 (alternate interior angles theorem, alternate exterior angles theorem, vertical angles theorem, definition of supplementary angles)
m∠7 + m∠8 = 180° (linear pair theorem, verticals angles theorem, same side interior angles theorem, alternate exterior angles theorem)
m∠2 + m∠8 = 180° (Substitution Property)
∠2 and ∠8 are supplementary (definition of supplementary angles)