=(7/19+12/19)+(3/11+8/11)+7/19

=1+1+7/19

=45/19

=7\19(8\11+3\11)+12\19

=7\19.11\11+12\19

=7\19+12\19

=19\19

=1

a) (- 25) x 125,4 x (-8) x (-17)

= (- 25 x 4) x (- 8 x 125) x (-17)

= (-100) x (-1000) x (-17)

= - 1 700 000

b) \(\frac{-3}{4}+\frac{2}{7}+\frac{-1}{4}+\frac{3}{5}+\frac{5}{7}\)

\(=\left(\frac{-3}{4}+\frac{-1}{4}\right)+\left(\frac{2}{7}+\frac{5}{7}\right)+\frac{3}{5}\)

\(=-1+1+\frac{3}{5}\)

\(=0+\frac{3}{5}=\frac{3}{5}\)

c) \(\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}-\frac{12}{19}\)

\(=\frac{7}{19}.\left(\frac{8}{11}+\frac{3}{11}\right)-\frac{12}{19}\)

\(=\frac{7}{19}.1-\frac{12}{19}\)

\(=\frac{7}{19}-\frac{12}{19}=\frac{-5}{19}\)

d) \(19\frac{5}{8}:\frac{7}{2013}-26\frac{5}{8}:\frac{7}{2013}\)

\(=\left(19\frac{5}{8}-26\frac{5}{8}\right):\frac{7}{2013}\)

\(=-7:\frac{7}{2013}\)

\(=-2013\)

e) \(\frac{-5}{12}.\frac{2}{11}+\frac{-5}{12}.\frac{9}{11}+\frac{5}{12}\)

\(=\frac{-5}{12}.\left(\frac{2}{11}+\frac{9}{11}\right)+\frac{5}{12}\)

\(=\frac{-5}{12}.1+\frac{5}{12}\)

\(=\frac{-5}{12}+\frac{5}{12}=0\)

~Học tốt~

\(A=\dfrac{7}{19}\cdot\dfrac{8}{11}+\dfrac{7}{19}\cdot\dfrac{3}{11}+\dfrac{12}{19}\\ A=\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)+\dfrac{12}{19}\\ A=\dfrac{7}{19}\cdot1+\dfrac{12}{19}\\ A=\dfrac{19}{19}=1\)

A = 7/19.8/11+7/19.3/11+12/19

A = 7/19. . (8/11 + 3/11) + 12/19

A = 7/19 . 1 + 12/19

A = 7/19 + 12/19

A = 1

Ta có: \(A=\dfrac{7}{19}\cdot\dfrac{8}{11}+\dfrac{7}{19}\cdot\dfrac{3}{11}+\dfrac{12}{19}\)

\(=\dfrac{7}{19}\cdot\left(\dfrac{8}{11}+\dfrac{3}{11}\right)+\dfrac{12}{19}\)

\(=\dfrac{7}{19}+\dfrac{12}{19}=1\)

A=7/19.8/11+7/19.3/11+12/19

A=7/19.(8/11+3/11)+12/19

A=7/19.1+12/19

A=7/19+12/19

A=1

Ai có lòng tốt

cho mình một 

tích đúng nhé.

Bài làm 

\(A=\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}+\frac{12}{19}\)

\(A=\frac{7}{19}.\left(\frac{8}{11}+\frac{3}{11}\right)+\frac{12}{19}\)

\(A=\frac{7}{19}.1+\frac{12}{19}\)

\(A=\frac{7}{19}+\frac{12}{19}\)

\(A=1\)

Bài làm

\(A=\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}+\frac{12}{19}\)

\(A=\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}+\frac{7}{19}.\frac{12}{7}\)

\(A=\frac{7}{19}.\left(\frac{8}{11}+\frac{3}{11}+\frac{12}{7}\right)\)

\(A=\frac{7}{19}\left(\frac{11}{11}+\frac{12}{7}\right)\)

\(A=\frac{7}{19}\left(1+\frac{12}{7}\right)\)

\(A=\frac{7}{19}\left(\frac{7}{7}+\frac{12}{7}\right)\)

\(A=\frac{7}{19}.\frac{19}{7}\)

\(A=1\)

Vậy A = 1 

A=7/19(8/11+3/11)+12/19

=7/19.1+12/19

=1

B=5/9(7/13+9/13-3/13)

=5/9.1

=5/9

ba đội công nhân có tất cả 192 người . số người đội 1 chiếm 1/4 tổng số. số người đội 2 bằng 125% đội 1. tính số người đội 3

\(\frac{7}{11}.\frac{8}{19}+\frac{7}{19}.\frac{3}{11}-\frac{12}{19}\)

\(=\frac{56}{209}+\frac{21}{209}-\frac{12}{19}\)

\(=\frac{7}{19}-\frac{12}{19}\)

\(=-\frac{5}{19}\)

kb vs tớ nha

và nhớ ủng hộ nữa đó

g: \(=\dfrac{-3}{4}-\dfrac{1}{4}+\dfrac{5}{7}+\dfrac{2}{7}+\dfrac{3}{5}=\dfrac{3}{5}\)

h: \(=\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)-\dfrac{12}{19}=\dfrac{7}{19}-\dfrac{12}{19}=-\dfrac{5}{19}\)

i: \(=\dfrac{2013}{7}\left(19+\dfrac{5}{8}-26-\dfrac{5}{8}\right)=\dfrac{2013}{7}\cdot\left(-7\right)=-2013\)

f: \(=\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)-\dfrac{12}{19}=\dfrac{7}{19}-\dfrac{12}{19}=\dfrac{-5}{19}\)

i: \(=\left(\dfrac{9}{24}-\dfrac{18}{24}+\dfrac{14}{24}\right)\cdot\dfrac{6}{5}+\dfrac{1}{2}=\dfrac{5}{24}\cdot\dfrac{6}{5}+\dfrac{1}{2}\)

=1/4+1/2=3/4

` 7/19 . 8/11 + 3/11 . 7/19 + (-12)/19 `

`= 7/19 . ( 8/11 + 3/11 ) + (-12)/19 `

`= 7/19 . 11/11 + (-12)/19`

`= 7/19 . 1 + (-12)/19 `

`= 7/19 + (-12)/19 `

`= -5/19 `

`( 3/8 + (-3)/4 + 7/12 ) : 5/6 + 1/2`

`= 3/8 + (-3)4 + 7/12 . 6/5 + 1/2`

`= ( 9+(-18) + 14)/24 . 6/5 + 1/2`

`= 5/24 . 6/5 + 1/2`

`= 1/4 + 1/2 `

`= 3/4`