Hey there!:
Density is the relationship between the mass and the volume of a material, at a given pressure and temperature.
Volume Displacement is now calculated :
Final volume - initicial volume
31.44 mL - 22.69 mL => 8.75 mL
Therefore:
D = m(g) / v (mL )
D = 23.625 / 8.75
D = 2.7 g/mL
Hope that helps!