In the figure AOB is a straight line then the value of $x$ is

60° 50° 40° 70°

40°

Note: An angle on straight line is always equals to 180° Hence, Sum of all given angles = 180° $(2x – 10)° + (x + 10)° + (x + 20)° = 180°$ $4x + 20° = 180°$ $x = 40°$