Cryptarithms are mathematical puzzles, where numbers are replaced by letters or symbols. Each letter represents a unique digit, and the challenge is to decode the puzzle using logical reasoning and arithmetic skills. Cryptarithms is also called as alphametics.
Example:
TT+TUT¯
 
Here, a single digit \(T\) is added \(3\) times, and it turns into a two-digit number \(UT\). That is, the unit digit of the resultant is again the same number \((T)\).
 
It is only possible when \(T\) is \(5\). 
 
\(5 + 5 + 5 = 15\)
 
Therefore, \(UT\) is \(15\).