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

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

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~

7/19 . 8/11 + 7/19 . 3/11 + 12/19

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

= 7/19 . 1 + 12/19

=7/19 + 12/19

= 1

Hi vọng các bạn nha

=(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)7/19.8/11+3/11.7/19+-12/19

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

=7/19.1+-12/19

=7/19+-12/19

=-5/19

a)

\(\dfrac{7}{19}\cdot\dfrac{8}{11}+\dfrac{3}{11}\cdot\dfrac{7}{19}+\dfrac{-12}{19}\\ =\dfrac{7}{19}\cdot\left(\dfrac{8}{11}+\dfrac{3}{11}\right)+\dfrac{-12}{19}=\dfrac{7}{19}\cdot1+\dfrac{-12}{19}=\dfrac{7}{19}+\dfrac{-12}{19}=\dfrac{5}{19}\)

\(\frac{7}{19}.\frac{8}{11}+\frac{7}{19}+\frac{12}{19}=\frac{7.8+7.11+12.11}{19.11}=\frac{256}{209}\)

265/209