
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 that the speed of the fast horse is twice that of the slow horse, and the time for the slow horse to deliver a document to a city 900 miles away is $x+1$ days, while the time for the fast horse to make the delivery is $x-3$ days, find the specified time $x$. Formulate an equation representing this situation.

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