The solubility of silver bromide can be increased by dissolving it in a solution containing the thiosulfate anion. AgBr(s) Ag+ (aq) + Br- (aq) K1 = 7.7 x 10-13 Ag+ (aq) + 2S2O3 2- (aq) Ag(S2O3)2 3- (aq) K2 = 4.7 x 1013 What is the value of the equilibrium constant for the overall reaction? AgBr(s) + 2S2O3 2-(aq) Ag(S2O3)2 3-(aq) + Br- (aq)  

I am not sure how to work this problem out. Can you please help?