You can
put this solution on YOUR website! .
I'd reformulate this problem as follows to avoid ambiguity:
--------------------------------------------------------------------------
The average of 9 numbers is 43. When one of the numbers is 
the new mean is 47. What is the number?
================================================================+
Solution
Since the average of 9 numbers is 43, their sum is 9*43 = 387.
Since the average of remaining 8 numbers is 47, their sum is 47*8 = 376.
Hence, the removed number is 387 - 376 = 11.
