
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
The total area of the four smaller rectangles must be equal to the area of the larger rectangle, and the areas of three of the smaller rectangles are 6, 15, and 25. Let x be the area of the shaded rectangle, and find x.

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