If triangle RST is congruent to triangle NPQ, then by corresponding parts of congruent triangles, RT is congruent to NQ.
When triangles RST and NPQ are congruent, their corresponding sides and angles are equal. Therefore, RT corresponds to NQ. In congruent triangles, corresponding parts, such as sides and angles, have equal measures. So, if triangle RST is congruent to triangle NPQ, then RT is congruent to NQ, meaning the length of RT is equal to the length of NQ.
This relationship is a fundamental property of congruent triangles, providing a basis for establishing equalities between corresponding elements. Consequently, the congruence of triangles RST and NPQ implies that RT is equal in length to NQ.