We can use a simple equation to solve this problem.
d = m/v
Where d is the density, m is the mass and v is the volume.
d = ?
m = 87.47 mg = 87.47 x 10⁻³ g
v = 0.03 mL
By applying the equation,
d = 87.47 x 10⁻³ g / 0.03 mL
d = 2.92 g/mL
Hence, the density of the mixture is 2.92 g/mL.