dear your question is not complete. bt i knw that this is rorkee 1992 problem.

 

H₂S--------> H⁺  +  HS^-  K_a1= 10^-7

 

HS---------> H⁺  +  S^2-   K_a2 =1.3 x10^-13

 

HCl----> H⁺ + Cl^-

 

now due to common ion effect the dissociation of H₂S is suppressed and the [H⁺] in the solution is due to HCl

 

K_a1  =  [H⁺][HS^-]

           ---------------

             [H₂S]

 

10^-7  =[0.3][HS^-]/[0.1]

 

Therefore [HS^-]= 3.3 x10^-8 M

 

Ka₂ =[H⁺] [S^2-]/[HS^-]

 

K_a1 x K_a2 =[H⁺]²[S²]/[H₂S]

 

Placing Ka1 and Ka2 in the obove expression we get [S^2-] as 1.4x10^-20 M