Use SAS to explain why ABC = DBC.

Explanation:
The figure shows us ...
AB ≅ DB
∠ABC ≅ ∠DBC
CB ≅ CB
In order, these are Side, Angle, Side in one triangle being shown congruent to corresponding Side, Angle, Side in the other triangle. This lets us conclude that ...
ΔABC ≅ ΔDBC by SAS