[tex] \frac{ {3}^{ - 2} - {3}^{ - 3} }{3} [/tex]
[tex] \frac{ \frac{1}{ {3}^{2} } - \frac{1}{ {3}^{3} } }{3} [/tex]
[tex] \frac{ \frac{1}{9} - \frac{1}{27} }{3} [/tex]
[tex] \frac{ \frac{2}{27} }{3} [/tex]
[tex] \frac{2}{81} [/tex]
