This requires stoichiometry.

Find the molar mass (g/mol) of Magnesium and Magnesium Oxide by using the periodic table.

Then, simply use dimensional analysis to solve for mass of MgO.

Start with the given information and convert from there. Also, note the mole ratio is 2:2 or 1:1.

0.52g * (mol / # g Mg) * (2 mol MgO / 2 mol O) * ( # g MgO / mol) = ?