(I)    ABC - DBB  = EFG
        +     +      +
(II)   ABB - ECC  = BBB
      -----------------
(III) DBEB - HBB  = IBC
       (IV)   (V)   (VI)


Solution:
(IV)     D = 1
(IV.1)   C = 0
(V.3)    H = E + 1  (no carry)
(I.3)    A = E + 2  (with carry, as no carry gives H)
(II.3)   A = E + B  (no carry)
Equating the last two equations shows
         B = 2
(IV.2)   E = 2B = 4
         A = 6
         H = 5
(I)      F = 9, G = 8
(III)    I = 7

       620 - 122  = 498
        +     +      +
       622 - 400  = 222
      -----------------
      1242 - 522  = 720


References:

Jürgen Köller;
  Cryptogramme,
  www.mathematische-basteleien.de