[tex]\bf \qquad \textit{Compound Interest Earned Amount}
\\\\
A=P\left(1+\frac{r}{n}\right)^{nt}
\qquad
\begin{cases}
A=\textit{compounded amount}\to &800\\
P=\textit{original amount deposited}\\
r=rate\to 7\%\to \frac{7}{100}\to &0.07\\
n=
\begin{array}{llll}
\textit{times it compounds per year}\\
\textit{monthly, meaning 12}
\end{array}\to &12\\
t=years\to &3\frac{1}{2}
\end{cases}[/tex]
solve for "P" to find the Principal