????????
      +---------
FHJWP | JHRYWJXW
       -FHJWP
        =====
        WUPLQJ
       - QYWJN
        ======
          XJHMX
         -YFNPJ
          =====
          FWWHRW
         -PGRFGH
          ======
          ??????

base: 15
letters: FGHJLMNPQRTUWXY
difficulty: medium
missing: T