Na2CO3 + 2HCl = CO2 + H2O + 2NaCl
this is the double displacement reaction
2 Na(+) + CO3(-2) + 2H(+) + 2Cl(-) ------> 2Na(+) + 2 Cl(-) + H2O + CO2
2Na+ and 2Cl- are the spectator ions as they appear on the both sides of equation :
so the net ionic equation can be written as :
CO3(-2) + 2H(+) -------------> H2O + CO2