Given the equilibrium system: pbco3(s) ↔ pb2 (aq) co32-(aq) which changes occur as pb(no3)2(s) is added to the system at equilibrium?

Answer is: the equilibrium  shifts toward the reactants, to the left side of chemical reaction.
It is because lead(II) nitrate dissociates in water:
Pb(NO₃)₂ → Pb²⁺(aq) + 2NO₃⁻(aq).
According to Le Chatelier's Principle, the position of equilibrium moves to counteract the change (more lead cations, common ion), the position of equilibrium will move so that the concentration of products decrease and concentration of reactants of chemical reaction increase.

Maybe you should get some from your teacher and learn more so you can get your grades up and maybe study a bit more