Hello!
As you can see, the angle is a straight angle, which measures 180°. One angle measures 80°.
180 - 80 = 100
That means the rest added all together measure 100°.
3x + 2x = 5x
5x = 100
Divide both sides by 5
[tex] \frac{5x}{5} = \frac{100}{5} [/tex]
[tex]\framebox{x = 20 \°}[/tex]
