Quadrilateral OPQR is inscribed in circle N, as shown below. Which of the following could be used to calculate the measure of ∠OPQ? Circle N is shown with a quadrilateral OPQR inscribed inside it. Angle O is labeled x plus 16. Angle P is not labeled. Angle Q is labeled 6x minus 4. Angle R is labeled 2x plus 16.

m∠OPQ + (2x + 16)° = 180°
m∠OPQ = (6x − 4)° + (2x + 16)°
m∠OPQ + (x + 16)° + (6x − 4)°= 360°
m∠OPQ = (x + 16)° + (6x − 4)°