There are several natural numbers (not 0), and the average value is 10. If the largest one is removed from these numbers, the remaining average is 9; if the smallest one is removed, the remaining average is 11. What is the largest number among these numbers?
有若干个自然数(都不为0)，平均值是10．若从这些数中去掉最大的一个，则余下的平均值为9；若去掉最小的一个，则余下的平均值为11．则这些数中最大的数最大可以是多少．
<gadget id="calculator">10 - 9</gadget>
<output>1</output>

<gadget id="calculator">9 / 1</gadget>
<output>9</output>

<gadget id="calculator">1 - 1</gadget>
<output>0</output>

<gadget id="calculator">9 + 0 + 9 + 1</gadget>
<output>19</output>

<result>19</result>