Answer:
20
Step-by-step explanation:
The line measures a total of 180°
So make an equation where all of the angles added together = 180
100 + 3x + x = 180
Then solve for x.
First, combine like terms.
100 + 4x = 180
Subtract 100 from both sides
4x = 80
Divide both sides by 4 to isolate x
x = 20
