.
. .
.
Subj:.....Find A Four Digit Number (S591) 
          From: Puzzles And Brain Teasers on 5/13/2008
Source: http://www.apuzzlezone.com/adailypuzzle/05-13-08.html

Find a four-digit number, with four different digits, that
equal to the number formed by its digits in descending order
minus the number formed by its digits in ascending order.
 
 
 
 

                  THE SOLUTION

                             6174
.
.
.