Answer:
[tex]\Large \boxed{\mathrm{5.71 \ g/cm^3 }}[/tex]
Step-by-step explanation:
[tex]\sf \displaystyle density = \frac{mass}{volume}[/tex]
[tex]\displaystyle \rho = \frac{m}{V}[/tex]
[tex]\sf Mass \rightarrow 20 \ g \\ Volume \rightarrow 3.5 \ cm^3[/tex]
[tex]\displaystyle \rho = \frac{20}{3.5}[/tex]
[tex]\rho \approx 5.71[/tex]