The molar mass of Allicin is 162 which means that you can just divide 64 by 162 since 64 is the mass of sulfur in 1 mole of Allicin (32×2=64). You should get 0.395 which is 39.5%.
I hope this helps. Let me know in the comment if anything is unclear. Also, were you supposed to use the values of carbon, hydrogen, and oxygen given? I didn't use them because I can't figure out how they can be the right ratios. 162 grams of Allicin should contains 72g of carbon, 10g of hydrogen, 16g of oxygen, and 64g of sulfur.