Answer
$\frac{27}{2}=13.5$
Work Step by Step
The sum of a infinite geometric sequence is given as: $ S=\dfrac{a_1}{1-r}$
Here, $ a_1=9$ and Common Ratio: $ r=\dfrac{1}{3}$
$ S=\dfrac{a_1}{1-r}$
Now,
$ S=\dfrac{9}{1-\dfrac{1}{3}}=\dfrac{27}{3-1}=\frac{27}{2}=13.5$
