Question

Are the triangles similar? If so, what postulate or theorem proves their similarity?

Yes, by ​SSS Similarity Theorem​

No, the triangles are not similar.

Yes, by ​ ​SAS Similarity Theorem​ ​

Yes, by ​AA Similarity Postulate​

Answer 1

Yes, by ​SSS Similarity Theorem​

Explanation:

If you observe each corresponding line segment (e.g. AB to DE), triangle DEF is basically triangle ABC but it's dilated by a scale factor 2, meaning that the line segments become 2 times as big. Since this holds true for all corresponding line segments, the triangles are similar by the SSS Similarity Theorem.