A 2.9-L sample of paint that has a density of 4.65 g/mL is found to contain 26.7 g Pb3N2(s). How many grams of lead were in the paint sample?

Answer 1

You don't need the density or volume of the paint.
Convert 26.7 g Pb3N2 to mols moles = grams/molar mass.

Moles Pb must be 3x moles Pb3N2.
grams Pb = mols Pb x molar mass Pb.