Answer: ASA
Step-by-step explanation:
The angles marked with a single arc are one pair of congruent angles forming one "A" of "ASA".
The other "A" is the angles marked with double arcs.
The "S" refers to the sides between those said angles. These sides overlap perfectly so we have a shared side, meaning they must be the same length (refer to the reflexive property).
This is why the triangles are congruent by the ASA (angle side angle) congruence theorem. One triangle is a reflected version of the other. The mirror line being that shared overlapping side. Congruent triangles are like twin identical copies.