In the given image, you have the following:
- side OP (first triangle) is congruent to side QR
- angle N is congruent to angle S
- angle O is congruent to angle Q
if angles N and S, and O and Q are equal, it is necessary that angles P and R are equal. Do to all interioir angles are equal, it is necessary that all sides of both trangles have the same length (beacuse one of such sides is equal to one side of the other triangle.)
Hence, you can conclude that both triangles are congruent:
ΔOPN ≅ ΔQRS
moreover, the specific theorem to express the congruent of both triangles is:
AAS