Answer
$b=\sqrt{195} \text{ } m$
Work Step by Step
Using $a^2+b^2=c^2$ or the Pythagorean Theorem, then,
\begin{array}{l}\require{cancel}
17^2+b^2=22^2
\\\\
289+b^2=484
\\\\
b^2=484-289
\\\\
b^2=195
\\\\
b=\pm\sqrt{195}
.\end{array}
Since there are no negative measurements, then $
b=\sqrt{195} \text{ } m
.$