A5.5 g sample of a substance contains only carbon and oxygen. carbon makes up 35% of the mass of the substance. the rest is made of oxygen. you are asked to determine the mass of oxygen in the sample. which of the following expressions demonstrates a mathematical procedure to solve this problem using the proper order of operations? 1) ((100 - 35)/100) times 5.5 grams = 2)100 - 35/100 times 5.5 grams = 3) 100 - (35/100) times 5.5 grams = *recall that to calculate a percent of an amount in grams means you have to convert the percent to a number and multiply by the amount in grams. for example, 50% means 50 out of 100, or 50 hundredths. so 50% of 10 grams is 0.50 times 10 grams. you need to take 0.50 and multiply it by 10 grams to determine 50% of 10 grams is 5.0. (50% and 10 grams are examples and not numbers for this problem.)