(I)       AB *   CD = EFCB
          *      +      -
(II)      EC +  GBB =  GEC
        ------------------
(III)   EBDB +  GCD = EDBD
        (IV)    (V)   (VI)



Solution:
(II.1)  B = 0


     90 *   64 = 5760
     *      +      -
     56 +  300 =  356
   ------------------
   5040 +  364 = 5404


     90 *   73 = 6570
     *      +      -
     67 +  200 =  267
   ------------------
   6030 +  273 = 6303


     90 *   82 = 7380
     *      +      -
     78 +  100 =  178
   ------------------
   7020 +  182 = 7202


References:

- Torsten Sillke;
  2003-11