№4. Выполните действия: a) 6\frac{2}{25}+7\frac{23}{25}-4\frac{1}{40}; б) 20\frac{1}{19}-4\frac{12}{19}-5\frac{17}{19}; в) (6\frac{5}{24}+7\frac{19}{24})-6\frac{19}{23}-5\frac{9}{23}.

№4. Выполните действия:

a) $$6\frac{2}{25}+7\frac{23}{25}-4\frac{1}{40}=(6+7-4)+(\frac{2}{25}+\frac{23}{25}-\frac{1}{40})=9+\frac{2}{25}+\frac{23}{25}-\frac{1}{40}=9+\frac{2+23}{25}-\frac{1}{40}=9+\frac{25}{25}-\frac{1}{40}=9+1-\frac{1}{40}=10-\frac{1}{40}=9+\frac{40}{40}-\frac{1}{40}=9+\frac{39}{40}=9\frac{39}{40}$$

Ответ: $$9\frac{39}{40}$$

б) $$20\frac{1}{19}-4\frac{12}{19}-5\frac{17}{19}=(20-4-5)+(\frac{1}{19}-\frac{12}{19}-\frac{17}{19})=11+\frac{1}{19}-\frac{12}{19}-\frac{17}{19}=11+\frac{1-12-17}{19}=11+\frac{-28}{19}=11-\frac{28}{19}=11-1\frac{9}{19}=10-\frac{9}{19}=9+\frac{19}{19}-\frac{9}{19}=9+\frac{10}{19}=9\frac{10}{19}$$

Ответ: $$9\frac{10}{19}$$

в) $$(6\frac{5}{24}+7\frac{19}{24})-6\frac{19}{23}-5\frac{9}{23}=(6+7)+(\frac{5}{24}+\frac{19}{24})-6\frac{19}{23}-5\frac{9}{23}=13+\frac{5+19}{24}-6\frac{19}{23}-5\frac{9}{23}=13+\frac{24}{24}-6\frac{19}{23}-5\frac{9}{23}=13+1-6\frac{19}{23}-5\frac{9}{23}=14-(6+5)-(\frac{19}{23}+\frac{9}{23})=14-11-\frac{19+9}{23}=3-\frac{28}{23}=3-1\frac{5}{23}=2-\frac{5}{23}=1+\frac{23}{23}-\frac{5}{23}=1+\frac{18}{23}=1\frac{18}{23}$$

Ответ: $$1\frac{18}{23}$$