Hi, I am doing this question and needed help on how a ratio would be calculated to get the empirical formula. I keep getting an empirical formula of CH2, the mark scheme says C3H7.
I understand that to get C3H7, you have to multiply by 3 but I dont understand why
Here is the question:

Analysis of a different hydrocarbon Y shows that it contains 83.7% by mass of carbon.
Calculate the empirical formula of Y.
Use this empirical formula and the relative molecular mass of Y (Mr = 86.0) to
calculate the molecular formula of Y.