Answer:
i bought it cuz i need a cup?
Explanation:
Answer: The coefficient for
is 12.
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

Thus in the reactants, there are 12 molecules of oxygen in balanced chemical equation. Thus the coefficient for
is 12.
Mg is magnesium. NO3 is nitrate. This gives you magnesium nitrate as an answer.