I need the answer and maybe someone can tell me how to do it? Please and Thanks!! :))

Answer:
83
Step-by-step explanation:
The 126 angle is an exterior angle of the triangle.
The 43 and x angles are the two remote interior angles of the 126 angle.
Theorem:
The measure of an exterior angle of a triangle equals the sum of the measures of the remote interior angles.
x + 43 = 126
x = 83
Answer:
x = 83
Step-by-step explanation:
The exterior angle of a triangle is equal to the sum of the opposite interior angles
126 = x+43
Subtract 43 from each side
126-43 = x+43-43
83 = x