There is a theorem for inscribed quadrilaterals in a circle. This theorem states that: "<span>Opposite angles in any quadrilateral inscribed in a circle are supplements of each other". In other words, the sum of each two opposite angles in a quadrilateral inscribed in a circle is 180.
Based on the above: measure angle O + measure angle Q = 180 measure angle R + measure angle P = 189
Therefore: measure angle P = 180 - measure angle R</span>
