????????
      +---------
7BC48 | A3CB28DD
       -7BC48
        =====
        145038
       -14A151
        ======
          3401D
         -47423
          =====
          17175D
         -16BC63
          ======
          ??????

base: 14
letters: 0123456789ABCD
difficulty: medium
missing: 9