(10 + 3x)° + (x - 30)° = 180°
(3x + x)° + (10 - 30)° = 180°
4x° - 20° = 180°
4x° = 180° + 20°
4x° = 200°
x° = 200/4
x° = 50°
So, the value of x is 50°
Hope it helps and is useful :)
