AAS postulate tells that if two angles and a non-included side of a triangle to equal to the two angles and a non-included side of another triangle then the two triangles are said to be congruent.
Given:- One angle and one side of a triangle is equal to the one angle and one side of the other triangle.
We see there is one more pair of equal angles as they are vertically opposite angles . [See the attachment]
⇒ there is a triangle where two angles and a non-included side of a triangle to equal to the two angles and a non-included side of another triangle then the two triangles are said to be congruent.