Systems of Differential Equations · Medium problem

A drug dose of $10$ mg is swallowed at $t=0$ (hours). The amount $x$ in the stomach and the amount $y$ in the bloodstream satisfy $x'=-2x,\ y'=2x-y$, with $x(0)=10,\ y(0)=0$. Find the largest amount of drug, in mg, that is ever in the bloodstream.