И) \(6\frac{3}{4} - \frac{5}{8}\)

\(6\frac{3}{4} - \frac{5}{8} = \frac{6 \times 4 + 3}{4} - \frac{5}{8} = \frac{27}{4} - \frac{5}{8}\)

Приводим к общему знаменателю 8:

\(\frac{27}{4} = \frac{27 \times 2}{4 \times 2} = \frac{54}{8}\)

\(\frac{54}{8} - \frac{5}{8} = \frac{54-5}{8} = \frac{49}{8} = 6\frac{1}{8}\)

Ответ: \(6\frac{1}{8}\).