I've been practicing this for my module in Jan, so hopefully this will be alright:
Essentially, you don't/shouldn't change the equation at all. You should work through the respective Relative Molecular Masses, and get yourself the answer - put things in brackets as you work it out and just get rid of them as you work out the contents - so for that you'd do the masses, and divide by 2 to gain the answer for one mole. Does that make any sense?