Opp. angles in a cyclic quadrilateral always add up to 180°

∠P + ∠R & ∠Q + ∠S = 180

x + x+y = 180 

2x + y = 180... i

2y - 30 + x = 180 

2y + x = 180 + 30

x + 2y = 210 ... ii

Elimination method:

(2x + y = 180) * 1 --> 2x + y = 180

(x + 2y = 210) * 2 --> 2x + 4y = 420

Subtracting both equations

- 3y = - 240

y = 80°

using eqn i

2x + y = 180

2x + 80 = 180

2x = 100

x = 50°