\(\dfrac{3}{11}\text{×}\dfrac{7}{19}+\dfrac{3}{11}\text{×}\dfrac{10}{19}+\dfrac{3}{11}\text{×}\dfrac{1}{19}=\dfrac{3}{11}\text{×}\left(\dfrac{7}{19}+\dfrac{10}{19}+\dfrac{2}{19}\right)=\dfrac{3}{11}\text{×}1=\dfrac{3}{11}\)

a) \(19\times\left(52+38\right)-9\times\left(52+38\right)=\)

\(=\)     \(19\times90-9\times90\) 

\(=90\times\left(19-9\right)\) 

\(=90\times10\) 

\(=900\) 

b) \(\dfrac{2}{5}\div\dfrac{3}{7}\times\dfrac{3}{7}\div\dfrac{2}{5}+2019=\)

\(=\left(\dfrac{2}{5}\div\dfrac{2}{5}\right)\times\left(\dfrac{3}{7}\div\dfrac{3}{7}\right)+2019\) 

\(=1\times1+2019\) 

\(=2019\)

7/19x(1/3+2/3)

=7/19x1

=7/19

NHỚ K CHO MÌNH NẾU ĐÚNG NHÉ

= 7/19x(1/3+2/3)

= 7/19x1

= 7/19

:)))))))

3/7×25/19-2/7×18/19

75/133-36-133

39/133

\(\dfrac{2}{3}+\dfrac{7}{13}-\dfrac{17}{9}+\dfrac{19}{13}-\dfrac{1}{9}+\dfrac{7}{3}\)

\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)-\left(\dfrac{17}{9}+\dfrac{1}{9}\right)\)

\(=\dfrac{9}{3}+\dfrac{26}{13}-\dfrac{18}{9}\)

\(=3+2-2\)

\(=3\)

\(\frac{3}{7}x\frac{25}{19}-\frac{1}{7}x\frac{18}{19}\)

\(=\left(\frac{3}{7}-\frac{1}{7}\right)x\left(\frac{25}{19}-\frac{18}{19}\right)\)

\(=\frac{2}{7}x\frac{7}{19}\)

\(=\frac{14}{133}\)

19/37+1-19/37

=(19/37-19/37)+1

=0+1

=1

9/8-(17/7-3/7)+7/8

=(9/8+7/8)-(17/7-3/7)

=2-2

=0

1/2+3/4+1/2

=(1/2+1/2)+3/4

=1+3/4

=7/4

19/37 + 1 - 19/37 = (19/37 - 19/37) + 1 = 1

9/8 - (17/7 - 3/7) + 7/8 = (9/8 + 7/8) - (17/7 - 3/7) = 16/8 - 14/7 = 2 - 2 = 0

1/2 + 3/4 + 1/2 = (1/2 + 1/2) + 3/4 = 1 + 3/4 = 7/4

a, 19/37+1-19/37

= (19/37-19/37)+1

=1

b, 9/8- (17/7-3/7)+7/8

= (9/8+7/8) - (17/7-3/7)

=16/8 - 14/7

= 2 - 2

=0

c, 1/2+3/4+1/2

= (1/2+1/2)+3/4

=1+3/4

=7/4

`( 9 xx 6 xx 5 xx 7 )/( 19 xx 7 xx 2 xx 3 )`

`= ( 9 xx 2 xx 3 xx 7 xx 5 )/( 19 xx 7 xx 2 xx 3 )`

`= (9xx5)/19` 

`= 45/19` 

= 9 x 6 x 5 x 7/19 x 7 x 2 x3