TITLE: How to solve a puzzle with numerals
QUESTION [7 upvotes]: Any insights are welcome for this puzzle.

The following equation is wrong: $103 - 102 = 3$. Move one numeral to make it correct. The numeral moved is: $0,1,2$ or $3$?

REPLY [2 votes]: Alternative solution: use Roman numerals:
CIII - CII = III
         ^
         move this one

CIIII - CI = III
    ^
    to here

(or
CIII - CII = III
               ^
               move this one

CIIII - CII = II
    ^
    to here

)