Mass of magnesium is 32.63-32.14=0.49g, mass of oxygen=32.95-32.63=0.32g.
So how many moles do you have? Divide mass by the atomic weight of magnesium (24.3), and you get 0.0201.
Divide g of oxygen by atomic weight (16.0), and you get a mole number of 0.0200.
Divide by the small quantity to get an integer ratio for at least one element, and you get a ratio of Magnesium to oxygen as 1.005:1
Therefore seeing as the difference is so small, you round off the 0.05 to make it a 1:1 ratio, hence MgO