2.193. Выполните действие: а) 1/5 + 1/7; б) 1/3 + 2/7; в) 3/5 + 5/6; г) 8/9 − 2/5; д) 5/12 + 1/6; е) 3/5 − 4/15; ж) 19/21 − 11/15; з) 5/42 + 10/63; и) 11/21 + 2/26; к) 5/24 − 7/60.

Приведём дроби к общему знаменателю и выполним действия.

1. \(\frac{1}{5}+\frac{1}{7}=\frac{7+5}{35}=\frac{12}{35}\).
2. \(\frac{1}{3}+\frac{2}{7}=\frac{7+6}{21}=\frac{13}{21}\).
3. \(\frac{3}{5}+\frac{5}{6}=\frac{18+25}{30}=\frac{43}{30}=1\frac{13}{30}\).
4. \(\frac{8}{9}-\frac{2}{5}=\frac{40-18}{45}=\frac{22}{45}\).
5. \(\frac{5}{12}+\frac{1}{6}=\frac{5}{12}+\frac{2}{12}=\frac{7}{12}\).
6. \(\frac{3}{5}-\frac{4}{15}=\frac{9-4}{15}=\frac{5}{15}=\frac{1}{3}\).
7. \(\frac{19}{21}-\frac{11}{15}=\frac{95-77}{105}=\frac{18}{105}=\frac{6}{35}\).
8. \(\frac{5}{42}+\frac{10}{63}=\frac{15+20}{126}=\frac{35}{126}=\frac{5}{18}\).
9. \(\frac{11}{21}+\frac{2}{26}=\frac{11}{21}+\frac{1}{13}=\frac{143+21}{273}=\frac{164}{273}\).
10. \(\frac{5}{24}-\frac{7}{60}=\frac{25-14}{120}=\frac{11}{120}\).

Ответ: а) \(\frac{12}{35}\); б) \(\frac{13}{21}\); в) \(1\frac{13}{30}\); г) \(\frac{22}{45}\); д) \(\frac{7}{12}\); е) \(\frac{1}{3}\); ж) \(\frac{6}{35}\); з) \(\frac{5}{18}\); и) \(\frac{164}{273}\); к) \(\frac{11}{120}\).