The remainder can be defined for all real numbers $x$ and $y$ with $y \neq 0$ by $$\text{rem} (x ,y)=x-y\left \lfloor \frac{x}{y} \right \rfloor$$ where $\left \lfloor \dfrac{x}{y} \right \rfloor$ denotes the greatest integer less than or equal to $\dfrac{x}{y}$ . What is the value of $\text{rem}\left(\dfrac{3}{8}, -\dfrac{2}{5}\right)$ ?