What is the empirical formula for this substance?

Baco₃

The first answer simply restates the molar ratios and is not in an acceptable form as a formula. The common method is to divide each molar ratio by the smallest of the numbers in the list of molar ratios. In simple problems like this, it is easier to multiply the molar ratios by 2, 3, 4, etc., until results close to whole numbers are obtained. This is especially true if the work must be done without a calculator. In this instance, doubling the molar ratios gives new ratios of 1.08 : 1.16 : 3.04, which is very close to 1: 1 : 3. It is also the smallest ratio of whole numbers that will work another important point.