Solving for the percent composition by mass of sulfur . The formula would be: \%S=m mass of sulfur / mass of compound x 100% Plugging in our data: \%S=32 amu / amu x 100% 0.266666 * 11 100% \%S=26.66 % Rounded off to two significant numbers it will be 27%. Therefore the answer is number 2 .