Final answer:
The most likely equation to calculate ∠OPQ would involve concepts from the Inscribed Angle Theorem and the sum of angles in a quadrilateral, making option (c) a potential answer; nevertheless, without further information, one cannot definitively select the appropriate equation for ∠OPQ from the options provided.
Step-by-step explanation:
To calculate the measure of ∠OPQ in quadrilateral OPQR inscribed in circle N, one must understand concepts from circle geometry such as the Inscribed Angle Theorem. This theorem states that the measure of an inscribed angle is half the measure of its intercepted arc. None of the provided options directly employ this theorem, but the correct equation might involve the sum of angles in a quadrilateral which is always 360° or the fact that opposite angles of an inscribed quadrilateral are supplementary. Therefore, option (c) which states m∠OPQ + (x + 16)° + (6x - 4)° = 360° seems to acknowledge this fact as it resembles the sum of angles in a quadrilateral. However, without further context on the relationship between these angle expressions, it's not possible to definitively choose the exact equation used to calculate ∠OPQ only from the options given.