Answer:
2SF₄ (g)  +  O₂ (g)  →  2OSF₄(g)
2 moles of sulfur tetrafluoride reacts with 1 mol of oxygen to make 2 moles of tetrafluoride monoxide
Explanation:
2SF₄ (g)  +  O₂ (g)  →  2OSF₄(g)
As we have two oxygens in reactants, we add 2 moles of OSFâ‚„. That made us to put a 2 in SFâ‚„ to ballance it, so we finally get 2 S, 8 F and 2 O in reactants and the same numbers in products.