The value of x in the diagram is 55°
Angles formed on parallel lines are formed when a transversal cut through parallel line(s).
This angles can be adjascent, corresponding , opposite and alternate to each other.
In the diagram ;
x - 30 + 3x - 10 = 180° ( adjascent angles on a straight line)
4x - 40 = 180
4x = 180 + 40
4x = 220
divide both sides by 4
x = 220/4
x = 55°
Therefore, the value of x is 55°