To balance the equation involving KMnO₄ and MgS, we first need to identify the correct stoichiometric coefficients for each compound. The balanced equation will have coefficients that maintain the same number of each type of atom on both sides. The correct coefficients are 2 for KMnO₄, 1 for MgS, 2 for K₂S, and 1 for Mg(MnO₄)₂. Thus, the balanced equation is: 2 KMnO₄ + MgS → K₂S + Mg(MnO₄)₂.