+118723 $$\begin{array}{rll}
4883.5&=&775(1+\frac{r}{12})^{12/4}\\\\
4883.5&=&775(1+\frac{r}{12})^3\\\\
\frac{4883.5}{775}&=&(1+\frac{r}{12})^3\\\\
\left(\frac{4883.5}{775}\right)^{1/3}&=&1+\frac{r}{12}\\\\
\left(\frac{4883.5}{775}\right)^{1/3}-1&=&\frac{r}{12}\\\\
12\times\left(\left(\frac{4883.5}{775}\right)^{1/3}-1\right)&=&r\\\\
r&=&12\times\left(\left(\frac{4883.5}{775}\right)^{1/3}-1\right)\\\\
\end{array}$$
$${\mathtt{12}}{\mathtt{\,\times\,}}\left({\left({\frac{{\mathtt{4\,883.5}}}{{\mathtt{775}}}}\right)}^{\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)}{\mathtt{\,-\,}}{\mathtt{1}}\right) = {\mathtt{10.164\: \!489\: \!991\: \!486\: \!86}}$$
If this is meant to be a compound interest answer then I think you made a mistake with how you used the formula!
+118723 $$\begin{array}{rll}
4883.5&=&775(1+\frac{r}{12})^{12/4}\\\\
4883.5&=&775(1+\frac{r}{12})^3\\\\
\frac{4883.5}{775}&=&(1+\frac{r}{12})^3\\\\
\left(\frac{4883.5}{775}\right)^{1/3}&=&1+\frac{r}{12}\\\\
\left(\frac{4883.5}{775}\right)^{1/3}-1&=&\frac{r}{12}\\\\
12\times\left(\left(\frac{4883.5}{775}\right)^{1/3}-1\right)&=&r\\\\
r&=&12\times\left(\left(\frac{4883.5}{775}\right)^{1/3}-1\right)\\\\
\end{array}$$
$${\mathtt{12}}{\mathtt{\,\times\,}}\left({\left({\frac{{\mathtt{4\,883.5}}}{{\mathtt{775}}}}\right)}^{\left({\frac{{\mathtt{1}}}{{\mathtt{3}}}}\right)}{\mathtt{\,-\,}}{\mathtt{1}}\right) = {\mathtt{10.164\: \!489\: \!991\: \!486\: \!86}}$$
If this is meant to be a compound interest answer then I think you made a mistake with how you used the formula!
