a) $6\cdot a^2=150c{m}^2\to a=5cm$  

$V=a^3=125c{m}^2$

b) $6\cdot a^2=60d{m}^2\to a=\sqrt{10}dm$ $6\cdot a^2=60d{m}^2\to a=\sqrt{10}dm$  

$V=a^3=\sqrt{10}d{m}^3=10\sqrt{10}d{m}^3$

c) $6\cdot a^2=288c{m}^2\to a=\sqrt{48}cm$  

$V=a^3={\sqrt{48}}^3=48\sqrt{48}c{m}^3$