I can’t give you the answer right now (because I don’t have my calculator, I’m on my phone) but I can tell you what to do.
For the first one you’re already given the amount of moles so you find the molar mass of C20H42 then you multiply the amount of moles to whatever the molar mass is.
For the second one find the molar mass of dinitrogen trioxide (N2O3). Then divide the mass by the molar mass.