There are two formulas that you need to know:
1. Circumference (length of the circle): [tex]C = 2 \pi r[/tex]
2. Length of the arc: [tex]l = ra[/tex],
where r is the radius and a is the angle.
Basically, you need only second formula there to find the answer. Let's use 63 as r, [tex]2 \pi /9[/tex] as a:
[tex]l = \frac{63 * 2 \pi }{9} = 7 * 2 \pi = 14 \pi = 44[/tex]
So, the answer will be 44 or [tex]14 \pi [/tex]
