With emily‘s employee discount she is charged $12 for the $15 item what is ella employee discount

here is the question in picture form.

what is the reason for step 3 of this proof?

a.   alternate interior angles theorem

b.   corresponding angles in congruent triangles are congruent.

c.   for parallel lines cut by a transversal, corresponding angles are congruent.

d.   vertical angles theorem

e.   sas criterion for congruence