Answer:
The answer to your question is   CH₄ + 2O₂  ⇒  CO₂  +  2H₂O
Explanation:
Data
Methane = CHâ‚„
Oxygen = Oâ‚‚
Process
A combustion reaction is a kind of chemical reaction in which an organic compound reacts with oxygen to generate water and carbon dioxide.
Chemical reaction
          CH₄ + O₂  ⇒  CO₂  +  H₂O
       Reactants  Elements   Products
          1          C         1
          4          H         2
          2          O         3
Balanced chemical reaction
          CH₄ + 2O₂  ⇒  CO₂  +  2H₂O
       Reactants  Elements   Products
          1          C         1
          4          H         4
          4          O         4