Answer
$\$626.61$
Work Step by Step
According to the Compound Interest Formula, where $P$ is the principal (the amount deposited), $r$ is the annual interest rate, $n$ is the number of times the interest is compounded in one year, $t$ is the number of years, $A$ is the amount the loaner gets back after $t$ years:
$A=P\cdot(1+\frac{r}{n})^{n\cdot t}.$
Here
$800=P\cdot\left(1+\frac{0.07}{12}\right)^{12\cdot (3.5)}\\
\frac{800}{\left(1+\frac{0.07}{12}\right)^{12\cdot 3.5}}P\\
626.61=P$
