Hey there!
Na + O₂ → Na₂O
Balance O.
2 on the left, 1 on the right. Add a coefficient of 2 in front of Na₂O.
Na + O₂ → 2Na₂O
Balance Na.
1 on the left, 4 on the right. Add a coefficient of 4 in front of Na.
4Na + O₂ → 2Na₂O
Our final balanced equation: 4Na + O₂ → 2Na₂O
Hope this helps!
