A Gallery of Groups · Easy problem

A linear map $T:\mathbb R^2\to\mathbb R^2$ is given by $T(v)=Av$, where $A=\begin{pmatrix}1&2\\0&1\end{pmatrix}\in GL(2,\mathbb R)$. Find the point $v=(x,y)$ with $T(v)=(5,3)$, and give $x+y$.