Ответ:

Блок 1. \(\frac{51}{20}-\frac{1}{4}=\frac{51}{20}-\frac{5}{20}=\frac{46}{20}=\frac{23}{10}\).

Блок 2. \(\frac{15}{4}\cdot\frac{6}{5}=\frac{9}{2}\).

Блок 3. \(\left(\frac{5}{26}-\frac{3}{25}\right)\cdot\frac{13}{2}=\left(\frac{125}{650}-\frac{78}{650}\right)\cdot\frac{13}{2}=\frac{47}{650}\cdot\frac{13}{2}=\frac{47}{100}\).