How do we find these angles? Someone please explain.Watch
Circle Theorems have never been my friend.
In R, Using the cyclic quadrilaterial rule in circle theorem you should see that Q + O = 180 degrees so 180 -115 = 65 degrees. Using that, you can work out the angle of ROS.
It should be clear that angle POR is not 65 degrees.
But I think this method is confusing for most students.