2.193. Выполните действия: а) 1/5 + 1/7; б) 1/3 + 2/7; в) 3/5 + 5/6; г) 3/9 − 2/5; д) 5/12 + 1/8; е) 3/5 − 4/15; ж) 19/21 − 11/15; з) 11/21 + 2/28; и) 5/42 + 10/63; к) 5/24 − 7/60.

1. \(\frac15+\frac17=\frac7{35}+\frac5{35}=\frac{12}{35}\).
2. \(\frac13+\frac27=\frac7{21}+\frac6{21}=\frac{13}{21}\).
3. \(\frac35+\frac56=\frac{18}{30}+\frac{25}{30}=\frac{43}{30}=1\frac{13}{30}\).
4. \(\frac39-\frac25=\frac13-\frac25=\frac5{15}-\frac6{15}=-\frac1{15}\).
5. \(\frac5{12}+\frac18=\frac{10}{24}+\frac3{24}=\frac{13}{24}\).
6. \(\frac35-\frac4{15}=\frac9{15}-\frac4{15}=\frac15\).
7. \(\frac{19}{21}-\frac{11}{15}=\frac{95}{105}-\frac{77}{105}=\frac6{35}\).
8. \(\frac{11}{21}+\frac2{28}=\frac{22}{42}+\frac3{42}=\frac{25}{42}\).
9. \(\frac5{42}+\frac{10}{63}=\frac{15}{126}+\frac{20}{126}=\frac5{18}\).
10. \(\frac5{24}-\frac7{60}=\frac{25}{120}-\frac{14}{120}=\frac{11}{120}\).

Ответ: а) 12/35; б) 13/21; в) 1 13/30; г) −1/15; д) 13/24; е) 1/5; ж) 6/35; з) 25/42; и) 5/18; к) 11/120.