Hello!! I need help on this problem on my math. . . -.-

And, you may think this is a easy math problem. But- It isn't. Cause- it's confusing?
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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