????????
      +---------
UJJMX | XMHUUXJQ
       -UJJMX
        =====
        FLWUJX
       -GXXXML
        ======
         QXTMXJ
        -QWWWJL
         ======
          QHWJJQ
         -FJUUJH
          ======
          ??????

base: 12
letters: FGHJLMQTUWXY
difficulty: intermediate
missing: Y