Calculate the percentage, by mass, of carbon in cyclohexane. Give your answer to two significant figures.

formua of cyclohexane C₆H₁₂ 

molar ratio is 1:2  (divide 6 and 12 by 6 )

to get mass ratio multiply by molar mass (1 x 12 and 2x1)

12:2

convert to percentage (12/14 = 6/7 = 85.7% carbon by mass  )