Final answer:
Without additional information, we cannot determine the length of side PR in triangle PQR, even though the two triangles are congruent and have the same perimeter.
Step-by-step explanation:
The question refers to two congruent triangles, MNO and PQR. If the perimeter of triangle MNO is 23 inches, this implies that the perimeter of triangle PQR is also 23 inches, since congruent triangles have sides of equal length. Unfortunately, without knowing the individual lengths of the sides of triangle MNO, we cannot determine the length of side PR in triangle PQR. We would need either the lengths of sides MN, NO, and OM or an additional piece of information about the relationship between the sides of triangle PQR.