Answer
$\frac{127}{8}=15.875$
Work Step by Step
The general formula to find the sum of a finite geometric sequence is given as: $ S_{n}=\dfrac{a_1(1-r^n)}{1-r}$
Here, $ a_1=8$ and $ r=\dfrac{1}{2}$
Plug $ n=15$
$ S_{n}=\dfrac{a_1(1-r^n)}{1-r}$
Now, $ S_{7}=\dfrac{8 \times [1-(\dfrac{1}{2}]^7)}{1-(\dfrac{1}{2})}=\frac{127}{8}=15.875$
