Answer
$|b-52.5|\le2.5$
Work Step by Step
Half-way between the given values, $
50\text{ and } 55
,$ is
\begin{array}{l}\require{cancel}
\dfrac{50+55}{2}
\\\\=
\dfrac{105}{2}
\\\\=
52.5
.\end{array}
The distance from $
52.5
$ to $50$ and to $55$ is $
2.5
.$
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 b \le55
,$ is equivalent to
\begin{array}{l}\require{cancel}
|b-52.5|\le2.5
.\end{array}
