Answer:
the answer is 74.03%
Step-by-step explanation:
Add all the masses together, M of C = 120.1, M of H = 14.4 and M of N = 28.02. Adding all those together will give you the mass of the compound, then u divide the mass of carbon by the mass of compound and multiply by 100 to get the percent by mass.
120.1 + 14.4 + 28.02 = 162.26
120.1/162.26 x 100 = 74.03%