Answer:
2CH4 - - - > C2H6+3H2O
2C2
8H12
0O3
6CH4 + 3O - - - > 3C2H6+3H2O
6C6
24H24
3O3
I added oxygen to the reactant side because I presumed this must be a combustion of methane; since, H2O is made in the product side.
Hope this helps!
