The balanced chemical reaction would be written as follows:
2Mg + O2 = 2MgO
We are given the amount magnesium to be used in the reaction. This will be the starting point for the calculations. We do as follows:
15.0 g ( 1 mol / 24.31 g ) (2 mol MgO / 2 mol Mg ) (40.31 g / mol ) = 24.87 g MgO formed
Answer:0.0185676392573
Explanation: 4+3=7 and 13x29=377 and 7/377=0.0185676392573
Failure allows you to learn that making mistakes is contrary for you to learn how to avoid making mistakes like that again. You can't avoid something if you don't even know where it's coming from, so you need to make the mistake of not avoiding it to know how to avoid it next time.
The answer is the last one :)