You have 11 numbers, and their average is 10. Average = sum of all numbers/# of numbers. This means that the sum of all the numbers is equal to 11*10=110.
Next, if you take away one of the numbers, you'll have 10 numbers, whose average is 9.3. Do the calculation from the first part again to find the sum of the remaining 10 numbers: 10*9.3=93.
To find the value of the number eliminated, just subtract the number from the sum of all numbers in second part after the elimination from the one in the first before the elimination: 110-93=?