Respuesta :

Answer:

x=12

Step-by-step explanation:

Using the external angle theorem (external angle = sum of interior angles that are NOT adjacent to the external angle you are finding), we can set up an equation...

140=3x+4+8x+4

Start by combining like terms...

140=11x+8

Subtract 8 from both sides

132=11x

Divide both sides by 11

x=12