The idea here is that the density of the object tells you the mass of
In this case, you know that the density is equal to
This implies that your sample will have a mass of
#10 color(red)(cancel(color(black)("cm"^3))) * "7.2 g"/(1color(red)(cancel(color(black)("cm"^3)))) = "72 g"#
Now, notice that you have one significant figure for the volume of the object. This implies that the answer must be rounded to one significant figure.
#"mass" = color(darkgreen)(ul(color(black)("70 g")))#