How do i solve this chemical equation?

The balanced equation must be:

2Na +  MgF₂  →  2NaF  +  Mg

Explanation:

You see that you have 2F in the reactant side, that's why we add 2, to the stoichiometry of the sodium fluoride.

So now, we have 2 moles of NaF. Therefore we need to add 2 to the sodium on the reactant side.

The equation is now balanced.

2 Na reactant side → 2 Na product side

1 Mg reactant side → 1 Mg product side

2 F product side → 2 F product side