Write a balanced equation for the following reaction. Use whole number coefficients and subscripts appropriately.

When hydrochloric acid is mixed with sodium hydrogen carbonate, the mixture fizzes. The fizzing occurs because the reaction produces a gas, namely carbon dioxide. The other products are a solution of sodium chloride and liquid water.

2 answers

HCl + NaHCO3 = NaCl + H2O + CO2
I would like to clarify Steve's answer a little. Since the question is so detailed about the phases I suspect the author of the question wants you to include the phases like this.
HCl(aq) + NaHCO3(s) --> H2O(l) + NaCl(aq) + CO2(g)