
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 a list of numbers 
\[18, 3, 5, 3, 7, 3, x, 12\]
where the mean, median, and mode are arranged in increasing order, and they form a non-constant arithmetic progression, determine the sum of all possible values of $x$.
A) 15
B) 22
C) 37
D) 44
E) 52

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