Answer
$9840$
Work Step by Step
Formula to calculate the sum of the first $n$ terms of a geometric sequence is: $s_n=\dfrac{a(1-r^n)}{(1-r)}$
Here, $r=\dfrac{a_2}{a_1}=3$
As we are given that, $n=8$
Thus, $s_{8}=\dfrac{3(1-3^{8})}{(1-3)}$
or, $s_{8}=9840$