This chemical formula represents a reaction pathway involving methane $CH4$, carbon dioxide $CO2$, and calcium bicarbonate $Ca(HCO3)3$. The "X" in the formula could represent a reactive intermediate or an unknown species involved in the overall reaction. The pathway starts with the reaction of methane with carbon dioxide to form an intermediate species, followed by the formation of calcium bicarbonate through a series of reactions. The overall reaction pathway involves the transformation of methane and carbon dioxide into calcium bicarbonate.