Ta có: \(\frac94\times\frac{15}{11}+\frac34:\frac{11}{7}-\frac34\times\frac{8}{11}\)

\(=\frac34\times\frac{45}{11}+\frac34\times\frac{7}{11}-\frac34\times\frac{8}{11}\)

\(=\frac34\times\left(\frac{45}{11}+\frac{7}{11}-\frac{8}{11}\right)=\frac34\times\frac{44}{11}=3\)

\(\dfrac{9}{4}\times\dfrac{15}{11}+\dfrac{3}{4}:\dfrac{11}{7}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times3\times\dfrac{15}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\dfrac{45}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\left(\dfrac{45}{11}+\dfrac{7}{11}-\dfrac{8}{11}\right)\)
\(=\dfrac{3}{4}\times4\)
\(=3\)

`9/4xx15/11+3/4:11/7-3/4xx8/11`

`=3/4xx15/11xx3+3/4xx7/11-3/4xx8/11`

`=3/4xx45/11+3/4xx7/11-3/4xx8/11`

`=3/4xx(45/11+7/11-8/11)`

`=3/4xx4`

`=3`

`a)17/7-3/8+4/7-3/5`

`=(17/7+4/7)-(3/8+3/5)`

`=21/7-(15/40+24/40)=3-39/40=120/40-39/40=81/40`

`b)15/11xx2001/2005-3/11xx2001/2005-1/11xx2001/2005`

`=2001/2005xx(15/11-3/11-1/11)`

`=2001/2005xx11/11`

`=2001/2005`

sfdhg 

Câu a:

4/15 x 7/8 + 4/15 x 2/9

= 4/15 x (7/8 + 2/9)

= 4/15 x (63/72 + 16/72)

= 4/15 x 79/72

= 79/270

a.\(\dfrac{18}{15}+\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{18+7+12}{15}=\dfrac{37}{15}\)

b.\(\dfrac{9}{7}+\dfrac{8}{7}+\dfrac{11}{7}=\dfrac{9+8+11}{7}=\dfrac{28}{7}=4\)

 a,  \(\dfrac{5\times11\times15\times18}{6\times15\times22\times10}\)

= \(\dfrac{5\times11\times15\times6\times3}{6\times15\times11\times2\times2\times5}\)

= \(\dfrac{5\times11\times15\times6}{5\times11\times15\times6}\) \(\times\) \(\dfrac{3}{2\times2}\)

= 1 \(\times\) \(\dfrac{3}{4}\)

= \(\dfrac{3}{4}\)

b, \(\dfrac{7}{12}\) \(\times\) \(\dfrac{3}{5}\) + \(\dfrac{3}{5}\) \(\times\) \(\dfrac{5}{12}\)

= \(\dfrac{3}{5}\) \(\times\) ( \(\dfrac{7}{12}+\dfrac{5}{12}\))

= \(\dfrac{3}{5}\) \(\times\) \(\dfrac{12}{12}\)

= \(\dfrac{3}{5}\) \(\times\) 1 

= \(\dfrac{3}{5}\)

a: \(245\times11+11\times365\)

=11x(245+365)

=11x610

=6710

b: \(78\times75+75\times89+75\times123\)

\(=75\times\left(78+89+123\right)\)

=75x290

=21750

c: \(2\times250\times50\times8\)

=2x50x250x8

=100x2000

=200000

d: (76:7)x4

=76x4:7

=304/7

e: (372x15)x9

=5580x9

=50220

f: (56x23x4):7

=56:7x23x4

=8x92

=736

a: \(\frac{5}{11}\times\frac{7}{25}+\frac{15}{11}\times\frac15\)

\(=\frac{7}{11\times5}+\frac{3}{11}=\frac{7+3\times5}{11\times5}=\frac{22}{55}=\frac25\)

b: \(\frac37\times\frac{25}{19}-\frac17\times\frac{18}{19}\)

\(=\frac{75}{7\times19}-\frac{18}{7\times19}=\frac{57}{7\times19}=\frac37\)

a) 18/15 + 7/15 + 12/15 =18/15 + 12/15 + 7/15        

                                    = 30/15 + 7/15

                                     =       37/15

b) 9/7 + 8/7 +11/7 = 9/7 + 11/7 + 8/7 

                         =  20/7  + 8/7 =  28/7 nha . tk mk nhé b

a, 18/15+7/15+12/15= 37/15

b, 9/7+8/7+11/7=28/7=4