Question

http://prntscr.com/ayuyf6 @abdullahM

Answer 1

n=9

Answer 2

What do you mean by n = 9?

Answer 3

What is the starting value of the counter, n?
What is the value of the first term?
What is the common ratio, r?
I'd suggest you first ignore the n=3 and find the sum of the first 12 terms of this geometric series. Do you know the formula for the nth term of a geometric series?

Once you've done that, find the first and second terms, add them, subtract this sum from the sum of the first 12 terms of the series, and you'll be done. Show your work for feedback.