The correct way to do it is to make use of angle PQR.
From the properties of angles within a circle, we know that angle 2PQR = angle ROP
Therefore, angle PQR = 110/2 = 55
Now, from quadrilaterals inscribed within a circle, the sum of two opposite angles = 180 degrees.
Therefore, 180 - 55 = RSP
And RSP = 125 degrees