
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
Three years ago, the population of Pirajussaraí was equal to the current population of Tucupira. Since then, the population of Pirajussaraí has remained unchanged, but the population of Tucupira has grown by $50\%$. Today, the combined population of the two cities is 9,000 inhabitants. What was the combined population of these two cities three years ago?
(a) 3600
(b) 4500
(c) 5000
(d) 7200
(e) 7500

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