
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 the speeds of a fast horse and a slow horse are related by a factor of 2, a document sent 900 miles away by the slow horse takes one day longer than the specified time, and the fast horse takes 3 days less than the specified time, derive the equation to solve for the specified time.

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