easy peasy
remember that the arc is a part of the perimiter of the circle aka circumference
also 360 degrees=circle
we are given the radius
calculate circumference
c=2pi times r
r=14
c=pi times 2 itimes 14
c=28pi
100 degrees is the arc
find what fraction of the circumferece thei srepresents
whole=360
100/360=10/36=5/18
so if circumference=28pi then multiply 5/18 by that
5/18 times 28pi=140pi/18=70pi/9
legnth=(70pi)/9 cm
if you were to aprox pi to 3.14 then the answer would be
24.4222222 cm