First, we have to divide the percentages by the atomic masses of the elements to get a ratio
Hydrogen: 2/1 = 2
Carbon: 74/12 = 6
Oxygen: 24/16 = 1.5
Now, to make sure that there are no decimals, we have to multiply the three numbers to make the 1.5 into 3
Hydrogen: 2 x 2 = 4
Carbon: 6 x 2 = 12
Oxygen: 1.5 x 2 = 3
So, the Empirical Formula is: C12H4O3
Hope I helped! xx
