The given angles in the image have the same measure becuase they are congruent angles.
Then, you equal both expression:
4 + 6x = 70
You solve the previous equation for x as follow:
4 + 6x = 70 subtract both sides by 4
6x = 70 - 4 simplify
6x = 66 divide by 6 both sides
x = 66/6
x = 11
Then, the solution for x is x = 11.