Answer
$|k-50.5|\le0.5$
Work Step by Step
Half-way between the given values, $
50\text{ and } 51
,$ is
\begin{array}{l}\require{cancel}
\dfrac{50+51}{2}
\\\\=
\dfrac{101}{2}
\\\\=
50.5
.\end{array}
The distance from $
50.5
$ to $50$ and $51$ is $
0.5
.$
Since $|x|\lt c$ implies $-c\lt x\lt c$ (or $|x|\le c$ implies $-c\le x\le c$), then the given inequality, $
50\le k \le51
,$ is equivalent to
\begin{array}{l}\require{cancel}
|k-50.5|\le0.5
.\end{array}
