Answer
$$5 \times 10^{-9} \mathrm{m}$$
Work Step by Step
Since$$\frac{1}{2} \mathrm{k} x^{2}=F$$
Then
\begin{aligned}
\frac{1}{2}\left(10^{-8}\right)^{2} \mathrm{k} &=10^{-17} \\
\mathrm{k} &=\frac{10^{-17}}{5 \times 10^{-17}} \\
&=\frac{1}{5} \mathrm{N} / \mathrm{m}
\end{aligned}
Hence \begin{aligned}
x&=\frac{F}{\mathrm{k}} \\
x&=\frac{10^{-9}}{0.2} \\
&=5 \times 10^{-9} \mathrm{m}
\end{aligned}
