A farmer owns sheep and chickens. All the sheep have 4 legs and the chickens have 2 legs. He has a total of 8 animals, and there is a total of 20 legs.

1) If $\displaystyle{x}\usepackage{cmbright}\Huge\$ is the number of sheep and $\displaystyle{y}\usepackage{cmbright}\Huge\$ is the number of chickens, write a system of equations that models this problem and graph it.

2) Determine the number of sheep and chickens.