Hey there!
B + O₂ → B₂O₃
Balance O.
2 on the left, 3 on the right. Add a coefficient of 3 in front of O₂ and a coefficient of 2 in front of B₂O₃.
B + 3O₂ → 2B₂O₃
Balance B.
1 on the left, 4 on the right. Add a coefficient of 4 in front of B.
4B + 3O₂ → 2B₂O₃
Our final balanced equation: 4B + 3O₂ → 2B₂O₃
Hope this helps!
