Using angle sum property for ΔPRT, we obtain
∠PRT + ∠RPT + ∠PTR = 180
40 + 95 + ∠PTR = 180
∠PTR = 180 − 135
∠PTR = 45
∠STQ = ∠PTR = 45 (Vertically opposite angles)
∠STQ = 45
By using angle sum property for ΔSTQ, we obtain
∠STQ+ ∠SQT + ∠QST = 180
45 + ∠SQT + 75 = 180
∠SQT = 180 − 120
∠SQT = 60