A.5/7

B.-481/391

C.0

D.-59/9

E.1

\(\dfrac{7}{-25}+\dfrac{18}{25}+\dfrac{4}{23}+\dfrac{5}{7}+\dfrac{19}{23}\)

=\(\left(\dfrac{-7}{25}+\dfrac{18}{25}\right)+\left(\dfrac{4}{23}+\dfrac{19}{23}\right)+\dfrac{5}{7}\)

= \(\dfrac{11}{25} +1+\dfrac{5}{7}\)

= \(1\dfrac{11}{25}+\dfrac{5}{7}\)

= \(2\dfrac{27}{175}\)

b) \(-2+\dfrac{15}{19}+\dfrac{-15}{17}+\dfrac{15}{23}+\dfrac{4}{19}\)

=\(-2+\left(\dfrac{ }{ }\right)\)

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1.25 . 7/19 + 5/4 . 15/19 - 5/4 : 19/3 =\(\frac{5}{4}\cdot\frac{7}{19}+\frac{5}{4}\cdot\frac{15}{19}-\frac{5}{4}\cdot\frac{3}{19}\)

                                                          \(\frac{5}{4}\left(\frac{7}{19}+\frac{15}{19}-\frac{3}{19}\right)=\frac{5}{4}=B\)

a) 12 + 3 = 15     15 + 4 = 19     8 + 2 = 10     14 + 3 = 17

15 - 3 = 12     19 - 4 = 15     10 - 2 = 8     17 - 3 = 14

b) 11 + 4 + 2 = 17     19 - 5 - 4 = 10     14 + 2 - 5 = 11

?

:>?

a: \(\dfrac{3}{5}-\dfrac{7}{4}=\dfrac{12}{20}-\dfrac{35}{20}=\dfrac{-23}{20}\)

b: \(\dfrac{4}{5}:\dfrac{-8}{15}=\dfrac{-4}{5}\cdot\dfrac{15}{8}=\dfrac{-60}{40}=\dfrac{-3}{2}\)

c: \(=7+\dfrac{5}{9}-2-\dfrac{3}{4}-3-\dfrac{5}{9}=2-\dfrac{3}{4}=\dfrac{5}{4}\)

d: \(=\dfrac{-3}{7}\left(\dfrac{4}{19}+\dfrac{15}{19}\right)+\dfrac{5}{7}=\dfrac{2}{7}\)

\(\dfrac{4}{19}\cdot-\dfrac{3}{7}+-\dfrac{3}{7}\cdot\dfrac{15}{19}+\dfrac{5}{7}\)

\(=-\dfrac{3}{7}\cdot\left(\dfrac{4}{19}+\dfrac{15}{19}\right)+\dfrac{5}{7}\)

\(=-\dfrac{3}{7}\cdot\dfrac{19}{19}+\dfrac{5}{7}\)

\(=-\dfrac{3}{7}+\dfrac{5}{7}\)

\(=\dfrac{-3+5}{7}\)

\(=\dfrac{2}{7}\)

=-3/7(4/19+5/19)+5/7

=5/7-3/7=2/7

` 4/19 . (-3)/7 + (-3)/7 . 15/19 + 5/7`

`= (-3)/7. ( 4/19 + 15/19 ) + 5/7`

`= (-3)/7 . 19/19 + 5/7`

`= (-3)/7 . 1 + 5/7`

`= (-3)/7 + 5/7`

`= 2/7`

=3/7(-4/19-15/19)+5/7

=-3/7+5/7=2/7