NGXW
      +---------
JPJXF | RFMRYNNY
       -YNYJM
        =====
        PMQMPN
       -PMFMYY
        ======
           QMGNY
          -GWGNN
           =====
           JPXXN

base: 11
letters: FGJMNPQRWXY
difficulty: intermediate
restrictions: no multiplication