\[\boxed{\mathbf{833\ (833).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[b_{n} = b_{1} \cdot q^{n - 1}\]
\[b_{8} = b_{7} \cdot q;\ \]
\[b_{13} = b_{1} \cdot q^{12} = b_{2} \cdot q^{11} = \ldots =\]
\[= b_{7} \cdot q^{6};\ \]
\[b_{60} = b_{7} \cdot q^{53}.\]