3. Вычислите: а) 5/14 + 6/21; б) 5/14 − 5/21; в) 17/30 + 11/70; г) 17/30 − 11/70; д) 9/22 + 2/121; е) 9/22 − 2/121.

а) \(\frac{5}{14}+\frac{6}{21}=\frac{15}{42}+\frac{12}{42}=\frac{27}{42}=\frac{9}{14}\).

б) \(\frac{5}{14}-\frac{5}{21}=\frac{15}{42}-\frac{10}{42}=\frac{5}{42}\).

в) \(\frac{17}{30}+\frac{11}{70}=\frac{119}{210}+\frac{33}{210}=\frac{152}{210}=\frac{76}{105}\).

г) \(\frac{17}{30}-\frac{11}{70}=\frac{119}{210}-\frac{33}{210}=\frac{86}{210}=\frac{43}{105}\).

д) \(\frac{9}{22}+\frac{2}{121}=\frac{99}{242}+\frac{4}{242}=\frac{103}{242}\).

е) \(\frac{9}{22}-\frac{2}{121}=\frac{99}{242}-\frac{4}{242}=\frac{95}{242}\).

Ответ: а) \(\frac{9}{14}\); б) \(\frac{5}{42}\); в) \(\frac{76}{105}\); г) \(\frac{43}{105}\); д) \(\frac{103}{242}\); е) \(\frac{95}{242}\).