How many solutions does this system have?

$\displaystyle{x}+{y}+{z}={4}\usepackage{cmbright}\Huge\$

$\displaystyle-{3}{x}-{3}{y}-{3}{z}=-{4}\usepackage{cmbright}\Huge\$

$\displaystyle{2}{x}+{2}{y}+{2}{z}={4}\usepackage{cmbright}\Huge\$