
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
There are 6 sealed boxes, each containing balls of only one color: red, white, or black. The number of balls in each box is 15, 16, 18, 19, 20, and 31, respectively. It is known that the number of black balls is twice the number of red balls, and there is only one box with white balls. 

Questions:
1. What color are the balls in the box containing 15 balls?
2. How many boxes contain black balls?

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