????????
      +---------
5A752 | 94894AA2
       -11B19
        =====
        3A731A
       -30401B
        ======
         53784A
        -538253
         ======
           16312
          -5A752
           =====
           ?????

base: 12
letters: 0123456789AB
difficulty: challenging
hints: B << 4, 4 << 0