Question

Need help proving a line is parallel to a triangle

Answer 1

I need to prove that a proportional line passing through a triangle is parallel.
So what I did was I drew triangle ABC and the segment DE. I found that corresponding angles are congruent and said since those are congruent, the line is parallel. But I went to class today and was asked to give more information, mine was too vague (practice sheet for the near year to see if we remember geometry) and I am a bit stuck.... How else would I do it? I considered finding the heights