Possible to move a populated variable back into the stem?

[Bires]

For this exercise (determination of empirical formula) I need to multiply the mass of the sample 8.00 grams by the percentages of N (0.304) and O (0.696).

A 8.00 gram sample of a colorless gas is found to be 2.43 grams nitrogen and 5.57 grams oxygen.  It has a molar mass of 92.0 grams/mole.  What is the molecular formula of this gas? `N2O4`  (You do not need to use subscripts.)

What I would like to do is make the sample mass a variable 8.00 -->`m`  and the N and O masses results of that variable 2.43 --> m*0.304 and 5.57 --> m*0.696 .

In short, I want to be able to move a variable into the stem of an exercise.

Any possible way to accomplish this feat?