Code:
+SECHS
+SECHS
======
ZWOELF
- Z
- F
- W
- C
- L
- S
- H
- O
- E
Code:
+69476
+69476
======
138952
- Z must be 1 (since even 99999+99999 = 199998).
- E must be >=5, sinze W≠F
- F must be even
- W must be F+1
- F can't be zero, since Z=1 and W≠Z
- S must be > 5 since Z=1 and F≠0
- L must be odd since S>5
- None of the top letters can represent zero, as the corresponding sum would be the same letter or Z (1), which doesn't happen.
With these restraints, it's fairly easy to go through the possibilities.