
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 bag containing $2$ red balls, $4$ white balls, and $a$ yellow balls, all the balls are identical except for their colors. If one ball is randomly drawn from the bag, and the probability of it being a yellow ball is $\frac{1}{4}$, then $a=\_\_\_\_\_\_$.

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