$\\triangle abc\\cong\\triangle edc, ab = 8, bc = 5, dc=?$

Explanation:

Step1: Recall property of congruent triangles

If $\triangle ABC\cong\triangle EDC$, then corresponding sides are equal.

Step2: Identify corresponding sides

Side $BC$ in $\triangle ABC$ corresponds to side $DC$ in $\triangle EDC$.

Step3: Use given side - length

Since $BC = 5$ and $BC=DC$ (corresponding sides of congruent triangles), then $DC = 5$.

Answer:

5