Answer:
3Mg + Mn2O3 --> 3MgO + 2Mn
Step-by-step explanation:
To know whether an equation is balanced, make sure to count how many atoms of a specific element are in each side.
In these options, the only one that has the same amount on each side is option 2.
On the reactant side, we have:
3 Mg, 2 Mn, and 3 O
On the product side, we have:
3 Mg, 2 Mn, and 3 O
If you have a coefficient in front of the molecule, that means that there is that amount of each element. For example 3 MgO, there is 3 Mg and 3 O.
If you have a subscript (the small number) after the element, that means there is specifically that amount of atoms of that element. For example Mn2O3, there is specifically 2 Mn and 3 O.