The formula to find the volume is V = LHW, so here we got the thickness instead of the Weight, it's the same ig
So [tex]V = 10*6*4 = 240 cm^3 [/tex]
The formula to find the density is [tex]d = \frac{Mass}{Volume} [/tex]
So [tex]d = \frac{180}{240} = 0.75[/tex] (Always remember that Density have no unity)
Hope this Helps :D