Given that,

l₁ ‖ l �₂ and l₃ is transversal

∠1 = 3x (Vertically opposite angle)

y = ∠1 (Corresponding angle)

y = 3x (i)

y + x = 180^o (Linear pair)

3x + x = 180^o [From (i)]

4x = 180^o

x = 45^o

Therefore,

y = 3x = 3 * 45^o

= 135^o