what is the percent by mass of carbon in c3h8?

Question

A. 18.20%
B. 20.0%
C. 81.8%
D. 85.0%

I say A

Answer 1

I don't think so.
%Carbon = (3*atomic mass C/molar mass C3H8)*100 = ?

Answer 2

C. 81.8%

Answer 3

That's right. Now you do that other problem the same way.