<s>[INST] # Problem
An infinite geometric series can be written as $$\sum_{n=0}^{\infty}12\cdot \left(\frac{-7}{8}\right)^n.$$ The formula for an infinite geometric series is $S=\frac{a}{1-r}$ where $a$ is the first term and $r$ is the common ratio. What is the sum of the series?[/INST]