The balanced equation is as below
2 N₂O₃ → 2N₂ + 3O₂
Explanation
According to the law of mass conservation the number of atoms in reactants side must be equal the to the number of atoms in products side.
Therefore the balanced reaction above is balanced since the number of atoms in reactants side are equal to number of atoms in products side.
For there 4 atoms of N in reactants side and 4 in products side.