How do you determine the mass of an object that has a volume of 88.6 mL and a density of 9.77 g/mL?

Or: $\rho = \frac{m}{V} \to m = \rho \times V$
$m = 9.77 \frac{g}{\cancel{m L}} \times 88.6 \cancel{m L} = 865.622 g \approx 866 g$