[tex]6^{-2} +6^{-3} = (\frac{1}{6})^{2} + (\frac{1}{6})^{3} = \frac{1}{36} +\frac{1}{216} = \frac{6}{216} +\frac{1}{216} = \frac{7}{216}[/tex]
[tex]3^{-1} + 3^{-2} + 3^{-3} = \frac{1}{3} + \frac{1}{9} +\frac{1}{27} = \frac{9}{27} +\frac{3}{27} +\frac{1}{27} = \frac{13}{27}[/tex]
[tex]2^{0} - 2^{-1} - 2^{-2} = 1 - \frac{1}{2} - \frac{1}{4} = \frac{4}{4} - \frac{2}{4} -\frac{1}{4}= \frac{1}{4}[/tex]
