The given expression is,
[tex]\lvert n\rvert=3.5[/tex]So we know that, the absolute value of a number is its distance from the origin, say 0. SInce the distance cannot be expressed in negative values, absolute values are always expressed as positive numbers. FOr example,
[tex]\lvert-x\rvert=\lvert x\rvert=x[/tex]Therefore, the values that make the given expression true can be,
[tex]\lvert n\rvert=3.5\Rightarrow n=-3.5\text{ or n=3.5}[/tex]