Step 1 :To solve for $a$, we need to isolate $a$ on one side of the equation. We can do this by multiplying both sides of the equation by the reciprocal of $\frac{5}{4}$, which is $\frac{4}{5}$.
Step 2 :After executing the operation, we find that $a$ equals -4.0. This is the solution to the equation.
Step 3 :The solution to the equation is $a = \boxed{-4.0}$.