56. Вычислите: \(1\frac{1}{4}+\frac{5}{17}\cdot2\frac{4}{15}-2\frac{1}{8}:\frac{51}{56}\).

\[1\frac14=\frac54,\quad 2\frac4{15}=\frac{34}{15},\quad 2\frac18=\frac{17}{8}.\]

\[\frac54+\frac5{17}\cdot\frac{34}{15}-\frac{17}{8}:\frac{51}{56}=\frac54+\frac23-\frac{17}{8}\cdot\frac{56}{51}.\]

\[\frac{17}{8}\cdot\frac{56}{51}=\frac73,\quad \frac54+\frac23-\frac73=\frac54-\frac53=-\frac5{12}.\]

Ответ: \(-\frac5{12}\).