?????????
      +----------
70B93 | 424740BBB
       -9BAA2
        =====
         51540
        -70B93
         =====
         04B25B
        -060782
         ======
          B167BB
         -89A693
          ======
           0AA79B
          -060782
           ======
           ??????

base: 12
letters: 0123456789AB
difficulty: intermediate