Answer
$-6$ is a solution.
Work Step by Step
Substitute $-6$ to $x$ to obtain:
$\begin{align*}
21\div x &\ge-3.5\\
21\div (-6)&\ge-3.5\\
-3.5&\ge-3.5
\end{align*}$
The resulting statement above is true therefore $-6$ is a solution of the given inequality.
