б) $$ 6^{-1} + 3^{-2} = \frac{1}{6} + \frac{1}{3^2} = \frac{1}{6} + \frac{1}{9} = \frac{3}{18} + \frac{2}{18} = \frac{3+2}{18} = \frac{5}{18} $$
Ответ: $$\frac{5}{18}$$