Answer:
120°
Step-by-step explanation:
Set up a proportion of the circle circumference and angle to the arc length and central angle x:
[tex]\frac{18}{360} = \frac{6}{x}[/tex]
Solve for x:
[tex]18x = 2160[/tex]
[tex]x = 120[/tex]
Measurement of the central angle of the arc is 120°
