A double replacement is a chemical reaction that takes place in which two reactants swap cations or anions to produce two distinct products.
Whenever the cations representing one of the reactants interact with the anions from another reactant to produce an insoluble ionic compound, a precipitate occurs.
The balanced equation for the given reaction:
Learn more about double displacement reactions here:
The degree of the numerator (4) is larger than the degree of the denominator (3), so first you need to divide. (Added screenshot of long division procedure.)
Now the second term can be decomposed into partial fractions.