We are given with the components carbon, hydrogen and nitrogen. I believe the numbers are the number of moles of each element. we convert each number of mole to mass by multiplying by their respective molar weights. Carbon has 120 grams, hydrogen has 14 grams and nitrogen has 28 grams. The total is 162 grams. Carbon is 74.07 percent, hydrogen is 8.64 percent, and nitrogen is 17.28 percent by mass.