What is the empirical formula of a compound that contains 40 percent carbon, 6.7 percent hydrogen, and 53.3 percent oxygen?

For the empirical formula we assume the percentages to be the equivalent mass and divide all with the smallest mass

so we have

40/6.7=5.97=6

6.7/6.7=1

53.3/6.7=7.95=8

So the empirical formula of the Compound is C6HO8