1. Найдите значение выражения: 1) 7,59 + 4,8; 2) 19,4 − 13,54; 3) 9,04 · 5,7; 4) 4,56 : 5,7; 5) \(\frac{3}{8}+\frac{2}{7}\); 6) \(9\frac{7}{15}-4\frac{3}{20}\); 7) \(\frac{14}{15}\cdot\frac{20}{21}\); 8) \(2\frac{1}{2}:1\frac{2}{3}\).

1. \(7,59+4,8=12,39\).
2. \(19,4-13,54=5,86\).
3. \(9,04\cdot5,7=51,528\).
4. \(4,56:5,7=0,8\).
5. \[\frac{3}{8}+\frac{2}{7}=\frac{21}{56}+\frac{16}{56}=\frac{37}{56}.\]
6. \[9\frac{7}{15}-4\frac{3}{20}=5+\left(\frac{28}{60}-\frac{9}{60}\right)=5\frac{19}{60}.\]
7. \[\frac{14}{15}\cdot\frac{20}{21}=\frac{2}{3}\cdot\frac{4}{3}=\frac{8}{9}.\]
8. \[2\frac{1}{2}:1\frac{2}{3}=\frac{5}{2}:\frac{5}{3}=\frac{5}{2}\cdot\frac{3}{5}=\frac{3}{2}=1\frac{1}{2}.\]

Ответ: 1) 12,39; 2) 5,86; 3) 51,528; 4) 0,8; 5) \(\frac{37}{56}\); 6) \(5\frac{19}{60}\); 7) \(\frac{8}{9}\); 8) \(1\frac{1}{2}\).