Answer
$n-12$
Work Step by Step
The word "fewer" represents the meaning "less than". In order to say one variable, say $a $ less than $b$ by $x$ units, it is expressed that $a$ is equal to $b-x$ using subtraction operation symbol.
Similarly, for the word $12$ fewer than $n$ meaning $12$ less than $n$, the algebraic expression can be written as $n-12$. It infers that the considered number is less than the number $n$ by $12$ units.
