270. Найдите значение выражения, предварительно сократив дроби:

Решение:

1. \( \frac{25}{80} + \frac{15}{60} = \frac{5}{16} + \frac{1}{4} = \frac{5+4}{16} = \frac{9}{16} \)
2. \( \frac{20}{45} + \frac{26}{54} = \frac{4}{9} + \frac{13}{27} = \frac{12+13}{27} = \frac{25}{27} \)
3. \( \frac{36}{300} + \frac{12}{40} - \frac{350}{1000} = \frac{3}{25} + \frac{3}{10} - \frac{7}{20} = \frac{12+30-21}{100} = \frac{21}{100} \)
4. \( \frac{14}{24} - \frac{39}{90} + \frac{15}{100} = \frac{7}{12} - \frac{13}{30} + \frac{3}{20} = \frac{35-26+9}{60} = \frac{18}{60} = \frac{3}{10} \)
5. \( \frac{42}{120} + \frac{20}{32} - \frac{28}{160} = \frac{7}{20} + \frac{5}{8} - \frac{7}{40} = \frac{14+25-7}{40} = \frac{32}{40} = \frac{4}{5} \)
6. \( \frac{45}{72} - \frac{33}{144} - \frac{20}{64} = \frac{5}{8} - \frac{11}{48} - \frac{5}{16} = \frac{30-11-15}{48} = \frac{4}{48} = \frac{1}{12} \)

Ответ: 1) \( \frac{9}{16} \); 2) \( \frac{25}{27} \); 3) \( \frac{21}{100} \); 4) \( \frac{3}{10} \); 5) \( \frac{4}{5} \); 6) \( \frac{1}{12} \).