9. (5 points) There are 4 distinct natural numbers, their average is 10. The largest number is at least

保留源文本的换行和格式，翻译结果如下：

9. (5 points) There are 4 distinct natural numbers, their average is 10. The largest number is at least
12
【Analysis】There are 4 distinct natural numbers, their average is 10, and they are 4 distinct natural numbers. To find the largest number at least, these 4 numbers should be as close as possible. Therefore, 10 is equivalent to the average of the middle two numbers, so the middle two numbers are 9 and 11. The other two numbers are $9-1=8$ and $11+1=12$. Therefore, the largest number at least is 12. According to this, solve the problem.
【Solution】Solution: Since to make the largest number at least, these 4 numbers should be as close as possible, then 10 is equivalent to the average of the middle two numbers,
So the middle two numbers are $10-1=9$ and $10+1=11$,
Then the other two numbers are $9-1=8$ and $11+1=12$,
Therefore, the largest number at least is 12,
Answer: The largest number at least is 12.
So the answer is: 12.