predict the reaction, if any, that would occur if AgNo3 and KBr were mixed would any reaction occur if HBr was then added?

Answer 1

If solids are mixed together there is no reaction. If solutions are mixed the following occurs.
AgNO3(aq) + KBr(aq) ==> AgBr(s) + KNO3

The addition of HBr to the solutions will have no additional effect; if HBr is added to the solids the liquid allows the solid salts to form aqueous solutions and the reaction above takes place.