Ответ:

а) \(\frac37+\frac5{14}=\frac6{14}+\frac5{14}=\frac{11}{14}\).

б) \(\frac89-\frac7{12}=\frac{32}{36}-\frac{21}{36}=\frac{11}{36}\).

в) \(\frac{11}{50}-\frac3{25}+\frac1{20}=\frac{22}{100}-\frac{12}{100}+\frac5{100}=\frac{15}{100}=\frac3{20}\).

Ответ: а) \(\frac{11}{14}\); б) \(\frac{11}{36}\); в) \(\frac3{20}\).