The question asks for the length of the arc of a sector of 72°.
Then, you can apply this proportion, naming the curcumference C:
C / 360° = arc / 72°
=> arc = 72° * C / 360°
Now use C =75 in
=> arc = 72° * 75 in / 360 =.15 in
Answer: the length of the arc is 15 in.
