????????
      +---------
HTXUN | UCUHLLTH
       -MYXTN
        =====
         UCLLL
        -MYXTN
         =====
          UTXLT
         -MYXTN
          =====
           MNXTH
          -LHUCN
           =====
           ?????

base: 10
letters: CHLMNQTUXY
missing: Q
hints: Q << T
difficulty: medium