Explanation:
Let [tex]v[/tex] be the volume of the given material.
Let [tex]m[/tex] be the mass of the material.
Let [tex]d[/tex] be the density of the material.
Density of a material is defined as the ratio of its mass to its volume.
[tex]d=\frac{m}{v}[/tex]
Given,
[tex]m=45g\\v=15ml[/tex]
So,[tex]d=\frac{45}{15}=3gmL^{-1}[/tex]