Answer
$S_8=2,460$
Work Step by Step
The sequence $
\dfrac{3}{4},\dfrac{9}{4},\dfrac{27}{4},...
$ is a geometric sequence with $a_1=\dfrac{3}{4}$ and $r=3$. Using $S_n=\dfrac{a_1(1-r^n)}{1-r}$, then,
\begin{array}{l}
S_8=\dfrac{\dfrac{3}{4}(1-3^8)}{1-3}\\\\
S_8=\dfrac{\dfrac{3}{4}(-6,560)}{-2}\\\\
S_8=2,460
.\end{array}
