Step 1: Compare triangles.
In both triangles, the given angles are equal: \(80^\circ\) in \(\triangle ABC\) and \(80^\circ\) in \(\triangle DEF\).
Step 2: Check corresponding sides.
\[
\frac{AB}{DE} = \frac{2.5}{5} = \frac{1}{2}, \quad \frac{BC}{EF} = \frac{3}{6} = \frac{1}{2}
\]
Thus, the sides are proportional, and one angle is equal.
Step 3: Apply the SAS similarity criterion.
Hence, \(\triangle ABC \sim \triangle EDF\).
Step 4: Conclusion.
The correct symbolic relation is \(\triangle ABC \sim \triangle EDF\).