By which congruence property, the two triangles given are congruent?[[1]]

SSS congruence rule SSS stands for side side side. In this Criterion, If three sides of one triangle are equal to the three sides of another triangle, then the two triangles are congruent.

$$\begin{gathered} \Rightarrow And here in \angle ACB \& \angle ADB \\ \Rightarrow X=X \& Y=Y \\ \Rightarrow So, \angle ACB\cong ADB \end{gathered}$$