The equation that demonstrates the law of mass conservation is:
H₂ + O₂ → H₂O
This equation indicates that the mass of the reactants (H₂ and O₂) is equal to the mass of the product (H₂O).
However, it looks like there may have been a misunderstanding in the formatting of the equations you provided. If the correct representation of your choice is modified to include arrows for the reaction direction, it would help.
If you're looking for a correctly balanced equation representing mass conservation, please clarify or correct the formatting, and I will assist you further!