RTT
      +---------
JRLNN | XMJGFTME
       -XTJJEL
        ======
          LXNMM
         -JRLNN
          =====
           JNWEE
          -JRLNN
           =====
             WGX

base: 13
letters: EFGJLMNPRTUWX
hints: W << U, F + F = U
difficulty: medium
restrictions: no multiplication
missing: U P