Answer:
not similar
Explanation:
You want to know if ∆ABC is similar to ∆DEF, given side lengths of (6, 4, 6) and corresponding side lengths of (8, 6, 8).
Similarity
Polygons are similar if corresponding sides are proportional. That is, the ratios of corresponding sides are the same. Here, those ratios are ...
(6, 4, 6)/(8, 6, 8) = (3/4, 2/3, 3/4)
The ratios 3/4 and 2/3 are not the same, so corresponding sides are not proportional. The triangles are not similar.