WWT
       +---------
ERRTRR | EXEFEFRF
        -ERRTRR
         ======
          XEWEFR
         -ERRTRR
          ======
          WERTFRF
         -WERXWRR
          =======
             ETRF

base: 8
letters: EFGQRTWX
difficulty: medium
hints: G << F
missing: G Q