RGJ
       +---------
GLXJUX | FLGUXJGG
        -FFGHUC
         ======
          FCGLJG
         -GLXJUX
          ======
          GFXHJLG
         -GFRHGLC
          =======
            FCHCG

base: 10
letters: CFGHJLMRUX
difficulty: medium
restrictions: no multiplication
missing: M