so... doubling 5000 is just 10,000, thus
[tex]\bf \qquad \textit{Simple Interest Earned Amount}\\\\
A=P(1+rt)\qquad
\begin{cases}
A=\textit{accumulated amount}\to &\$10,000\\
P=\textit{original amount deposited}\to& \$5,000\\
r=rate\to 5.6\%\to \frac{5.6}{100}\to &0.056\\
t=years
\end{cases}
\\\\\\
10000=5000(1+0.056t)\implies \cfrac{10000}{5000}=1+0.056t
\\\\\\
2=1+0.056t\implies 1=0.056t\implies \cfrac{1}{0.056}=t[/tex]