[tex]~~~~~~ \textit{Simple Interest Earned} \\\\ I = Prt\qquad \begin{cases} I=\textit{interest earned}\dotfill & \$420\\ P=\textit{original amount deposited}\\ r=rate\to 6\%\to \frac{6}{100}\dotfill &0.06\\ t=years\dotfill &7 \end{cases} \\\\\\ 420 = (P)(0.06)(7)\implies \cfrac{420}{(0.06)(7)}=P\implies 1000=P[/tex]
