The value of $x$ here is,
${\mathrm{Na}}_2{\mathrm{CO}}_3+\mathrm{xHCl}\to 2\mathrm{NaCl}+{\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}.$

Sodium bicarbonate reacts with hydrochloric acid to produce sodium chloride, water, and carbon dioxide, and this reaction occurs stoichiometrically depending on the number of atoms present in the molecules of reactants.

When the number of atoms in the molecules of the reactants and products is all balanced, the reaction is said to be balanced.

Here, the only difference between the reactant and the product is the number of hydrogen and chlorine atoms. Because the number of hydrogen and chlorine atoms on the product side is two, the value of x on the reactant side is two.

${\mathrm{Na}}_2{\mathrm{CO}}_3+2\mathrm{HCl}\to 2\mathrm{NaCl}+{\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}$

Hence, the value of $x$ is 2.

Thus, the correct option is (B).