\[2^{- 3} + 6^{- 1} = \frac{1}{2^{3}} + \frac{1}{6} =\]
\[= \frac{1^{\backslash 3}}{8} + \frac{1^{\backslash 4}}{6} = \frac{3 + 4}{24} = \frac{7}{24}.\]