Anyone? i know it's an octagon but from there i'm stuck

Molly shared a spool of ribbon with 12 people. each person received 3 feet of ribbon. which equation can she use to find r, the number of feet of ribbon that her spool originally had?

What is the sum of the geometric series in which a1 = 7, r = 3, and an = 1,701? hint: cap s sub n equals start fraction a sub one left parenthesis one minus r to the power of n end power right parenthesis over one minus r end fraction comma r ≠ 1, where a1 is the first term and r is the common ratio

Estimate the time en route from majors airport (area 1) to winnsboro airport (area 2). the wind is from 340° at 12 knots and the true airspeed is 136 knots. magnetic variation is 5° east.