Final answer:
The additional congruence required to prove ΔABC ≅ ΔPOR by SSS congruence is that BC equals OR.
Step-by-step explanation:
To prove that ΔABC ≅ ΔPOR by the SSS congruence theorem, we need to establish that all three corresponding sides of the triangles are equal in length. Given that AC = PR and AB = PQ, we need to find the congruence of the third pair of corresponding sides to satisfy the requirements of SSS congruence. Therefore, the additional congruence required is:BC = OR