a)

`2/3+5/2-3/4`

`=10/4-3/4+2/3`

`=7/4+2/3`

`=21/12+8/12`

`=29/12`

b)

`2/5xx1/2:1/3`

`=2/10xx3/1`

`=6/10=3/5`

c)

`2/9:2/9xx1/3`

`=2/9xx9/2xx1/3`

`=1xx1/3`

`=1/3`

a, \(\dfrac{2}{3}\) + \(\dfrac{5}{2}\) - \(\dfrac{3}{4}\)

= \(\dfrac{8}{12}\) + \(\dfrac{30}{12}\) - \(\dfrac{9}{12}\)

= \(\dfrac{38-9}{12}\)

= \(\dfrac{29}{12}\)

b, \(\dfrac{2}{5}\) x \(\dfrac{1}{2}\) : \(\dfrac{1}{3}\)

= \(\dfrac{1}{5}\) x \(\dfrac{3}{1}\)

= \(\dfrac{3}{5}\)

c, \(\dfrac{2}{9}\) : \(\dfrac{2}{9}\) x \(\dfrac{1}{3}\)

= 1 x \(\dfrac{1}{3}\)

= \(\dfrac{1}{3}\)

Số cần tìm là 181 nha(Mình tính lộn cái BCNN)

`x+3/5=7/6`

`=>x=7/6-3/5`

`=>x=35/30-18/30`

`=>x=17/30`

x+3/5=7/6

x       =7/6-3/5

x       =35/30-18/30

x       =17/30

\(\dfrac{63}{45}-\dfrac{20}{25}=\dfrac{7}{5}-\dfrac{4}{5}=\dfrac{3}{5}\)

\(\dfrac{36}{21}-\dfrac{15}{20}=\dfrac{720}{420}-\dfrac{315}{420}=\dfrac{405}{420}=\dfrac{27}{28}\)

\(\dfrac{36}{21}-\dfrac{15}{20}=\dfrac{12}{7}-\dfrac{3}{4}=\dfrac{27}{28}\)

`2+3/4`

`=8/4+3/4`

`=11/4`

11/4

\(\dfrac{2}{5}+\dfrac{1}{4}=\dfrac{8}{20}+\dfrac{5}{20}=\dfrac{13}{20}\)
\(\dfrac{1}{3}+\dfrac{3}{5}=\dfrac{5}{15}+\dfrac{9}{15}=\dfrac{14}{15}\)
\(\dfrac{1}{2}+\dfrac{1}{4}=\dfrac{2}{4}+\dfrac{1}{4}=\dfrac{3}{4}\)
\(\dfrac{1}{8}+\dfrac{5}{6}=\dfrac{3}{24}+\dfrac{20}{24}=\dfrac{23}{24}\)

ĐÂSDWADAS

= 5/7 - 1/7 

= 4/6

mk lm lại ạ!

= 5/7 - 1/7

= 4/7

\(\dfrac{5}{11}-\left(\dfrac{3}{5}-\dfrac{6}{11}\right)\)
\(=\dfrac{5}{11}-\dfrac{3}{5}+\dfrac{6}{11}\)
\(=\left(\dfrac{5}{11}+\dfrac{6}{11}\right)-\dfrac{3}{5}\)
\(=1-\dfrac{3}{5}\)
\(=\dfrac{5}{5}-\dfrac{3}{5}\)
\(=\dfrac{2}{5}\)

`5/11-(3/5-6/11)`

`=5/11-3/5+6/11`

`=(5/11+6/11)-3/5`

`=1-3/5`

`=2/5`