I suppose that the question ask the following:
What is the mass of a sample, composed of C₃H₅N₃O₉ molecule, that contains 100 g carbon?
First we calculate the molecular mass of our molecule C₃H₅N₃O₉.
molecular mass = 12 × 3 + 1 × 5 + 14 × 3 + 16 × 9 = 227 g/mol
Now we devise the following reasoning:
if 227 g of our molecule contains 27 g of carbon
then X g of our molecule contains 100 g carbon
X = (100 × 227) / 27 = 840.7 g
