First, write a balanced equation for the chemical reaction:  2NaOH  +  H\(_2\)SO\(_4\) → Na\(_2\)SO\(_4\) + 2H\(_2\)O

From the balanced equation, N\(_A\) = 1 ; N\(_B\) = 2

C\(_A\) = 0.5 moldm\(^{-3}\)  ; V\(_A\) = ? ; C\(_B\) = 0.1 moldm\(^{-3}\) ;  V\(_B\) = 20 cm\(^3\)

Using the formula, \(\frac{{C_A}{V_A}}{{C_B}{V_B}}\) = \(\frac{N_A}{N_B}\)

  V\(_A\) = \(\frac{{C_B}{V_B}{N_A}}{{C_A}{N_B}}\)

 = \(\frac{{0.1}\times{20}\times{1}}{{0.5}\times{2}}\)

 V\(_A\) = 2.0 cm\(^3\)