There is one letter in error in the addition below.  How should this problem read in order to be solvable?  Except for this single wrong letter, the usual rules of such "encrypted" math problems apply:
  • the same letters stand for the same digits wherever they appear
  • different letters stand for different digits
  • no leading zeros.

XTMB + WHMW + TTMW + MXMB = BBBB


This was a difficult puzzle but David and his father Larry helped us solve it.  If you want you can read their solution or try to answer yourself and add a comment