Answer:
See explanation
Step-by-step explanation:
The sum of the first n terms of a geometric sequence is given by:
[tex]S_n= \frac{a(1 - {r}^{n} )}{1 - r} [/tex]
Where a=3 is the first term and n=8.
Unfortunately you missed out the common ratio r.
When the available information is substituted, we get:
[tex]S_8= \frac{3(1 - {r}^{8} )}{1 - r} [/tex]
If we had known the value of r, we would have simplified further.
