The solubility of salts of weak acids increases at lower pH. Can you explain the derivation in textbook?

A strong acid i.e high pH affects the solubility of a salt of a weak acid by providing hydronium (H3O+ ions) ion that reacts with the anion of the weak salt in the solution. As the anion is removed by the reaction with hydronium ions, more salt dissolves to replenish the anion concentration thus increasing the solubility of a weak salt at high pH.