Density (D) is the quotient obtained when mass (m) is divided by volume (v).
D = m / v
The volume is the difference of the volume read after and before the object is placed in the beaker,
v = 23.1 mL - 18.5 mL = 4.6 mL
Substituting the known values for the density,
D = 8.24 g / 4.6 mL = 1.79 g/mL
Thus, the density is approximately equal to 1.79 g/mL.