Concept:In a cyclic quadrilateral, the sum of each pair of opposite angles is 180∘.Explanation:For ∠PQR and ∠PSR:(5x−y+10)+(−2x+3y+145)=180Simplify:3x+2y+155=180⇒3x+2y=25(1)For ∠QPS and ∠QRS:(−4x−7y+150)+(2x+8y+105)=180Simplify:−2x+y+255=180⇒−2x+y=−75Thus:y=2x−75Substitute into equation (1):3x+2(2x−75)=253x+4x−150=25⇒7x=175⇒x=25Then:y=2(25)−75=−25Hence:x+y=25+(−25)=0Answer:x+y=0