1. Решить выражения: 1) 3/8 + 5/12; 2) 7/9 − 2/15; 3) 4/7 · 14/20; 4) 5/6 : 10/21; 5) 2 3/5 + 1 1/2; 1) 3,7 + 5,48; 2) 9,02 − 4,6; 3) 2,35 · 4,2; 4) 7,2 : 0,9; 5) (5,6 + 2,4) · 0,5 − 1,25.

Решение:

1. \(\frac{3}{8}+\frac{5}{12}=\frac{9}{24}+\frac{10}{24}=\frac{19}{24}\).
2. \(\frac{7}{9}-\frac{2}{15}=\frac{35}{45}-\frac{6}{45}=\frac{29}{45}\).
3. \(\frac{4}{7}\cdot\frac{14}{20}=\frac{56}{140}=\frac{2}{5}\).
4. \(\frac{5}{6}:\frac{10}{21}=\frac{5}{6}\cdot\frac{21}{10}=\frac{7}{4}=1\frac{3}{4}\).
5. \(2\frac{3}{5}+1\frac{1}{2}=\frac{13}{5}+\frac{3}{2}=\frac{26}{10}+\frac{15}{10}=\frac{41}{10}=4\frac{1}{10}\).

1. \(3,7+5,48=9,18\).
2. \(9,02-4,6=4,42\).
3. \(2,35\cdot4,2=9,87\).
4. \(7,2:0,9=8\).
5. \((5,6+2,4)\cdot0,5-1,25=8\cdot0,5-1,25=4-1,25=2,75\).

Ответ: 1) \(\frac{19}{24}\); 2) \(\frac{29}{45}\); 3) \(\frac{2}{5}\); 4) \(1\frac{3}{4}\); 5) \(4\frac{1}{10}\); 1) 9,18; 2) 4,42; 3) 9,87; 4) 8; 5) 2,75.