Let "x" be the number of atoms of oxygen. Then the number of atoms of hydrogen is 3x, and the number of atoms of carbon is 3x+4. Collecting altogether, we obtain H + O + C = 18 3x + x + (3x+4) = 18 ====> 7x + 4 = 18 ====> 7x = 18-4 = 14 ====> x == 2. Then the answer is: H O C 6 2 10. The chemical formula . Naphthoquinone ( From Wikipedia https://www.algebra.com/tutors/faq.mpl )