????????
      +---------
BA5B8 | A7060663
       -BA5B8
        =====
        8BA546
       -894055
        ======
          4B3B6
         -BA5B8
          =====
          5057A3
         -560596
          ======
          ??????

base: 12
letters: 0123456789AB
missing: 1 2
difficulty: hard
hints: 9 + A = 2