The average of several positive integers is 10. If the largest number is removed from these numbers, the average value of the remaining numbers is 9; if the smallest number is removed, the average value of the remaining numbers is 11. So, what is the largest of these numbers?
若干个正整数的平均值是10．若从这些数中去掉最大的一个数，则余下的数的平均值为9；若去掉最小的一个数，则余下的数的平均值为11．那么，这些数中最大的数是多少．
<result>18</result>