Lisa and Katie are playing a card game, and a total of 900 points has been scored. Lisa scored 400 more points than Katie. If you let $\displaystyle{l}=\usepackage{cmbright}\Huge\$ the number of points that Lisa scored, and $\displaystyle{k}=\usepackage{cmbright}\Huge\$ the number of points that Katie scored, then the problem can be represented by the system:

$\displaystyle{l}+{k}={900}\usepackage{cmbright}\Huge\$ and $\displaystyle{l}={k}+{400}\usepackage{cmbright}\Huge\$

Graph the system. How many points did each of them score?