
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
A biologist is assessing the fish population in a reservoir. On June 1, she captures, tags, and releases 100 fish. To understand population dynamics, she hypothesizes that 30% of these fish will have left the reservoir by October 1 due to natural factors, while 50% of the fish present in October were not there in June. On October 1, she captures another sample of 90 fish, finding that 4 of them are tagged. How many fish were in the reservoir on June 1 according to her model?

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