[tex](\frac{2}{3})^{3} - \frac{2}{3^{2}} = \frac{2^{3}}{3^{3}}-\frac{2}{3^{2}} = \frac{8}{27}-\frac{2}{9} = \frac{8}{27} -\frac{6}{27} = \frac{2}{27}[/tex]
