а)
\(\frac{1}{8}\)c - (\(\frac{5}{9}\)c - \(\frac{1}{4}\)c) = \(\frac{1}{8}\)c - \(\frac{5}{9}\)c + \(\frac{1}{4}\)c = (\(\frac{1}{8}\) - \(\frac{5}{9}\) + \(\frac{1}{4}\))c = (\(\frac{9}{72}\) - \(\frac{40}{72}\) + \(\frac{18}{72}\))c = -\(\frac{13}{72}\)c
Ответ: -\(\frac{13}{72}\)c