Solution # 1

Well here is the "logic" solution.

12, write it: = T  W  E  L  V  E

Now, we must sum 1, who's writing is O  N  E

The partial writing become:  T   W  E  L  V  E   O  N  E

Now we must subtract 2, who's writing is T  W  O

The global writing left (afetr taking off TWO) is likewise: E  L  V  E   N  E

If we slightly rearrange letters  (anagram) we obtain= E  L  E  V  E  N  !!

So we can say that in english summing numbers or letters is the same thing ...

Hope you enjoyed my dears...

A la prochaine...

Claudio