D

D

em cảm ơn ạ

\(=\dfrac{17}{2}+\dfrac{3}{5}\times\left(1+\dfrac{1}{2}+1\right)=\dfrac{17}{2}+\dfrac{3}{5}\times\dfrac{5}{2}=\dfrac{17}{2}+\dfrac{15}{10}=\dfrac{17}{2}+\dfrac{3}{2}=\dfrac{17+3}{2}=\dfrac{20}{2}=10\)

\(\dfrac{17}{2}+\dfrac{3}{5}+\dfrac{3}{5}\times\dfrac{1}{2}+\dfrac{3}{5}=\dfrac{17}{2}+\dfrac{3}{5}+\dfrac{3}{10}+\dfrac{3}{5}=\dfrac{85}{10}+\dfrac{6}{10}+\dfrac{3}{10}+\dfrac{6}{10}=10\)

cảm ơn hai bẹn

a,Ta có \(\frac{x}{6}=\frac{2}{3}\)

\(\Rightarrow3x=12\Rightarrow x=4\)

Vậy x = 4

b, \(\left(\frac{4}{7}+\frac{8}{9}\right)-\frac{5}{9}=\frac{4}{7}+\frac{8}{9}-\frac{5}{9}\)

\(=\frac{4}{7}+\left(\frac{8}{9}-\frac{5}{9}\right)\)

\(=\frac{4}{7}+\frac{1}{3}\)

\(=\frac{19}{21}\)

Bài 1 mình nhầm. x phần 6 = 4 phần 7 mới đúng. Cảm ơn bạn nhé

\(\dfrac{1}{2}+\dfrac{3}{5}+\dfrac{3}{4}+\dfrac{7}{25}=\left(\dfrac{2}{4}+\dfrac{3}{4}\right)+\left(\dfrac{15}{25}+\dfrac{7}{25}\right)=\dfrac{5}{4}+\dfrac{22}{25}=\dfrac{125}{100}+\dfrac{88}{100}=\dfrac{213}{100}=2\dfrac{13}{100}\)

\(\dfrac{1}{2}+\dfrac{3}{5}+\dfrac{7}{25}+\dfrac{3}{4}=\dfrac{11}{10}+\dfrac{7}{25}+\dfrac{3}{4}\)

                             \(=\dfrac{69}{50}+\dfrac{3}{4}\)

                             \(=\dfrac{213}{100}\)

\(\dfrac{1}{2}+\dfrac{3}{5}+\dfrac{7}{25}+\dfrac{3}{4}=\dfrac{50+60+28+75}{100}=\dfrac{213}{100}\)

19 x ( 52 + 38 ) - 9 x ( 52 + 38 )

= 19 x 90 - 9 x 90

= ( 19 - 9 ) x 90

= 10 x 90

= 900

\(\dfrac{2}{5}:\dfrac{3}{7}\times\dfrac{3}{7}:\dfrac{2}{5}+2019=\left(\dfrac{2}{5}:\dfrac{2}{5}\right)\times\left(\dfrac{3}{7}:\dfrac{3}{7}\right)+2019=1\times1+2019=1+2019=2020\)

=16/27

\(\frac{4}{3}:\frac{5}{4}:\frac{6}{5}:\frac{7}{6}:\frac{8}{7}:\frac{9}{8}\)

=\(\frac{4}{3}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)

=\(\frac{16}{27}\)   

       4/3 x 5/4 x 6/5 x 7/6 x  8/7 x 9/8 

   =  4/9