\(\dfrac{33}{38}:\dfrac{11}{19}=\dfrac{33\times19}{38\times11}=\dfrac{3\times1}{2\times1}=\dfrac{3}{2}\)

\(\dfrac{38}{45}-\left(\dfrac{8}{45}-\dfrac{17}{51}-\dfrac{3}{11}\right)\)

\(=\dfrac{38}{45}-\dfrac{8}{45}+\dfrac{17}{51}+\dfrac{3}{11}\)

\(=\dfrac{2}{3}+\dfrac{1}{3}+\dfrac{3}{11}\)

\(=1\dfrac{3}{11}\)

B1 :

a) \(\dfrac{2}{15}+3=\dfrac{2}{15}+\dfrac{15}{5}=\dfrac{17}{5}\)

b) \(2-\dfrac{7}{4}=\dfrac{8}{4}-\dfrac{7}{4}=\dfrac{1}{4}\)

c) \(\dfrac{17}{6}-\dfrac{11}{12}\times6=\dfrac{17}{6}-\dfrac{11}{2}=-\dfrac{8}{3}\)

d) \(\dfrac{14}{17}:7-\dfrac{15}{34}=\dfrac{2}{17}-\dfrac{5}{34}=\dfrac{4}{34}-\dfrac{5}{34}=-\dfrac{1}{34}\)

B3 :

\(x:23=146\)

\(x=146\times23\)

\(x=3358\)

b) \(x\times38=4066\)

\(x=4066:38\)

\(x=107\)

c) \(787+x\times67=2658\)

\(x\times67=2658-787\)

\(x\times67=1871\)

\(x=1871:67\)

\(x=\dfrac{1871}{67}\)

từng bài thôi 

tách ra

..... làm j thế

( \(\dfrac{13}{17}\) + \(\dfrac{4}{17}\) ) + (\(\dfrac{2}{13}\) + \(\dfrac{11}{13}\) ) = \(\dfrac{17}{17}\) + \(\dfrac{13}{13}\) = \(1\) + \(1\) = \(2\).

\(=\dfrac{-3}{17}-\dfrac{2}{13}+\dfrac{20}{17}-\dfrac{11}{13}\)

=1-1

=0

\(-\left(\dfrac{3}{17}+\dfrac{2}{13}\right)-\left(\dfrac{-20}{17}+\dfrac{11}{13}\right)\)

\(=-\dfrac{3}{17}-\dfrac{2}{13}-\dfrac{20}{17}-\dfrac{11}{13}\)

\(=-\left(\dfrac{3}{17}+\dfrac{20}{17}\right)-\left(\dfrac{2}{13}+\dfrac{11}{13}\right)\)

\(=-\dfrac{23}{17}-1\)

\(=-\dfrac{40}{17}\)

\(-\left(\dfrac{3}{17}+\dfrac{2}{13}\right)-\left(\dfrac{-20}{17}+\dfrac{11}{13}\right)\)

⇔ \(\dfrac{-3}{17}-\dfrac{2}{13}+\dfrac{20}{17}-\dfrac{11}{13}\)

⇔ \(\left(\dfrac{-3}{17}+\dfrac{20}{17}\right)+\left(\dfrac{-2}{13}-\dfrac{11}{13}\right)\)

⇔ \(1+\left(-1\right)\)

⇔ \(0\)

11/17×646/495

38/45

\(\frac{11}{17}\times\left(\frac{38}{45}\times\frac{17}{11}\right)\)

\(=\frac{11}{17}\times\frac{17}{11}\times\frac{38}{45}\)

\(=1\times\frac{38}{45}\)

\(=\frac{38}{45}\)

\(\frac{11}{17}\times\left(\frac{38}{45}\times\frac{17}{11}\right)\)

\(=\frac{11}{17}\times\frac{38}{45}\times\frac{17}{11}\)

\(=\frac{38}{45}\)

Linz

câu này có người làm r

Ko đăng lại nhé!

\(\dfrac{5}{17}\left(\dfrac{7}{11}+\dfrac{4}{11}\right)-\dfrac{12}{17}=\dfrac{5}{17}\times1-\dfrac{12}{17}=\dfrac{5}{17}-\dfrac{12}{17}=-\dfrac{7}{17}\)

`a)4/5+5 1/2 xx (4,5-2)+7/10`

`=4/5+11/2*2,5+7/10`

`=0,8+2,2+0,7`

`=3+0,7=3,7`

`b)125%xx 17/4:(1 5/16-0,5)+2008`

`=1,25xx4,25:13/16+2008`

`=85/13+2008`

`=2014 7/13`

`c)5/11+(16/11+1)`

`=5/11+1+5/11+1`

`=2+10/11=32/11`

`d)3/17+11/4+5/8+14/17+3/8`

`=3/17+14/17+5/8+3/8+11/4`

`=1+1+11/4`

`=19/4`

a) 

\(\dfrac{4}{5}+5\dfrac{1}{2}x\left(4,5-2\right)=\dfrac{7}{10}\)

<=> \(\dfrac{11}{2}x\times2,5=\dfrac{7}{10}-\dfrac{4}{5}=\dfrac{-1}{10}\)

<=> \(\dfrac{55}{4}x=\dfrac{-1}{10}< =>x=\dfrac{-2}{275}\)

b) \(125\%\times\dfrac{17}{4}:\left(1\dfrac{5}{16}-0,5\right)+2008\)

= \(\dfrac{85}{16}:\left(\dfrac{21}{16}-\dfrac{1}{2}\right)+2008=\dfrac{85}{16}:\dfrac{13}{16}+2008=\dfrac{26189}{13}\)

c) \(\dfrac{5}{11}+\left(\dfrac{16}{11}+1\right)\)

= \(\dfrac{21}{11}+1=\dfrac{32}{11}\)

d) \(\left(\dfrac{3}{17}+\dfrac{14}{17}\right)+\left(\dfrac{5}{8}+\dfrac{3}{8}\right)+\dfrac{11}{4}\)

= 1 + 1 + \(\dfrac{11}{4}\) = \(\dfrac{19}{4}\)