1. Вычислите: 1) 3/7 + 4/9; 2) 8/9 − 7/8; 3) 18/15 − 2/3; 4) 20/21 + 3/7; 5) 17/18 − 11/12; 6) 7/16 + 1/6; 7) 9/2 + 5/6; 8) 10/21 + 9/14; 9) 7/9 − 4/15.

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Accepted Answer

\(\frac{3}{7}+\frac{4}{9}=\frac{27}{63}+\frac{28}{63}=\frac{55}{63}\).
\(\frac{8}{9}-\frac{7}{8}=\frac{64}{72}-\frac{63}{72}=\frac{1}{72}\).
\(\frac{18}{15}-\frac{2}{3}=\frac{6}{5}-\frac{2}{3}=\frac{18-10}{15}=\frac{8}{15}\).
\(\frac{20}{21}+\frac{3}{7}=\frac{20}{21}+\frac{9}{21}=\frac{29}{21}=1\frac{8}{21}\).
\(\frac{17}{18}-\frac{11}{12}=\frac{34}{36}-\frac{33}{36}=\frac{1}{36}\).
\(\frac{7}{16}+\frac{1}{6}=\frac{21}{48}+\frac{8}{48}=\frac{29}{48}\).
\(\frac{9}{2}+\frac{5}{6}=\frac{27}{6}+\frac{5}{6}=\frac{32}{6}=5\frac{1}{3}\).
\(\frac{10}{21}+\frac{9}{14}=\frac{20}{42}+\frac{27}{42}=\frac{47}{42}=1\frac{5}{42}\).
\(\frac{7}{9}-\frac{4}{15}=\frac{35}{45}-\frac{12}{45}=\frac{23}{45}\).

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