If 3 grams of magnesium consume 2 grams of oxygen while burning, how much oxide will be formed?
I don't know what Holy Nsmr stands for but I can tell you it isn't chemistry. The SUBJECT goes there so a chemist can help. Otherwise most of us let it go. Here is a worked example of a stoichiometry problem. Just follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html