
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given an arithmetic sequence $\{a_{n}\}$ that satisfies $a_{3}=7$, $a_{5}+a_{7}=26$, and its sum of the first $n$ terms is $S_{n}$.
(I) Find the general term formula for $\{a_{n}\}$ and $S_{n}$;
(II) Let $b_{n}=\frac{1}{S_{n}-n} (n \in \mathbb{N}^*)$, find the sum of the first 8 terms of the sequence $\{b_{n}\}$.

Present the answer in LaTex format: \boxed{Your answer}
user