An Alphametic (also known as a Cryptorythm) is a puzzle form in which each letter stands for a distinct numeral. A famous example is
which has the additional nice property that what it says in words is true (auf Deutsch, that is). The solution, E=8, I=2, N=1, V=3 and R=4, is unique -- most good alphametics have this property!
An internet search will turn up many others, but here is a selection of the more interesting ones (in the humble opinion of your puzzle editor.)
This one is considered a classic:
SEND
+ MORE
--------
MONEY
Giving some equal time to the French:
VINGT
CINQ
+ CINQ
--------
TRENTE
The smallest one that makes sense in English:
THREE
THREE
TWO
TWO
+ ONE
--------
ELEVEN
With a nod to William S. :
DOUBLE
DOUBLE
+ TOIL
--------
TROUBLE
This one involves all the planets past Jupiter:
SATURN
URANUS
NEPTUNE
+ PLUTO
---------
PLANETS
Here's a couple involving multiplication:
TWO MAD
* TWO * MAN
-------- -------
THREE ASYLUM
Now that you've had a little practice, here is this semester's big puzzle.
In the following alphametic, each X represents a single digit which
must be a prime -- either 2,3,5 or 7 (obviously, the X's need not all be
the same!).
XXX
* XX
-------
XXXX
XXXX
-------
XXXXX