Question

Oxygen is 36.8% of a compound. What is the mass in grams of a sample of the compound that contains 21.8 g of oxygen?

Answer 1

(grams O/grams compd)*100 = 36.8

(21.8g O/grams compd)*100 = 36.8
Solve for grams compd
Or look at it another way,
36.8% of what number = 21.8