The figure given above shows us a circle with a couple of lines intersecting certain points on it. So if we divide the circle into two, then we have a semi circle with an angle of 180° on its vertical side. Since ∠ROP = 125°, then subtract 180° to 125° and you will get ∠POS = 55°. ∠POS is also equal to ∠QOR. And ∠ROP = ∠QOS.
