
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 $\overrightarrow{e}_{1}$ and $\overrightarrow{e}_{2}$ are two non-collinear vectors on a plane, $\overrightarrow{a}=x \overrightarrow{e}_{1}-3 \overrightarrow{e}_{2} (x \in \mathbb{R})$, and $\overrightarrow{b}=2 \overrightarrow{e}_{1}+ \overrightarrow{e}_{2}$. If $\overrightarrow{a} \parallel \overrightarrow{b}$, find the value of $x$.

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