Answer
$1.4\ cm$
Work Step by Step
We are given the mass and the density ($m=7.6\ g,\ \rho=2.698\ g/cm^3$), so the volume is :
$V=7.6 \div 2.698 = 2.8\ cm^3$
For a cube, the volume is given by $V=L^3$, so the length is:
$L=\sqrt[3]{2.8} = 1.4\ cm$
