Correct choice is (a) 160°
Easy explanation: As we know that sum of all the internal angles of the triangle is 180°.
Therefore x+y+z=180°
Therefore 30°+130°+z=180°
Therefore z=120°
Now we know that the external angle is always a linear angle.
Therefore x+y=180°
Therefore 20°+y=180°
Therefore y=160°.