????????
      +---------
XFEXP | TGLGUXCH
       -XFEXP
        =====
         XYTYX
        -XFEXP
         =====
          EXPPCH
         -EECPUX
          ======
          ??????

base: 12
letters: CEFGHLPQTUXY
missing: Q
difficulty: medium
hints: H << Q