PQ || AC ( given)
∠y = ∠BAC (alt. angles) …(i)
Again AB || RS (given)
∠BAC = ∠LMC …(ii) (corresponding angles)
From (i) and (ii), we get
∠LMC = ∠y
In ΔLMC, exterior angle is equal to sum of opposite interior angles
⇒ 80° = ∠y + 30°
⇒ ∠y = 80° – 30°
⇒ ∠y = 50°