How do I balance this

H2 + O2 = H2O

2 H2 + O2 = 2 H2O

Explanation:

H2 + O2 = H2O

- Left side: 2H and 2O

- Right side: 2H and 1O

Add a coefficient of 2 to the right side

H2 + O2 = 2 H2O

- Left side is still: 2H and 2O

- Right side now has: 4H and 2O

Add a coefficient of 2 to H2 on the left side

2 H2 + O2 = 2 H2O

- Left side still has: 4H and 2O

- Right side now has: 4H and 2O

2 H2 + O2 = 2 H2O is the balanced equation.