You haven't given any values, but, here's an example:
Write balanced equation:
2H2 + O2 → 2H2O
So, for each mole of H2 burned, a mole of H2O is produced and a half of a mole of O2 is consumed.
To turn moles into grams: mole x grams/mole (This is molar mass.)
To turn grams into moles: grams x mole/gram
For example, let there be 2.02 gram H2.
2.02 g H2 x (1 mole H2/2.02 g H2) x (1 mole O2/2 mol H2) X 32.00 g O2/1 mol O2) = 16.00 g O2