For example If I have to solve the following reaction numerically $$*\ce{ + A(g) <=>[K1] [A*]}$$

$$\ce{[A{*}]<=>[k1][k-1] [B{*}]}$$

$$\ce{[B*] <=>[K2] [B](g) +}*$$

Where the first and third reactions are fast equilibrium steps.

[* ] represents vacnt site and [A*] and [B*] represent adsorbed species.

The reaction is carried out in a closed container, therefore the concentrations of A(g) and B(g) are not constant. Given initial A(g) and B(g) pressure and assuming zero coverage of reactants initially, how do I solve a system like this numerically.