`5/39xx(7 4/5xx1 2/3+8 1/3xx7 4/5)`

`=5/39xx(39/5xx5/3+25/3xx39/5)`

`=5/39xx39/5(5/3+25/3)`

`=1xx30/3`

`=10`

10

10

\(\frac{2}{3}+\frac{5}{9}-\frac{3}{4}=\frac{24}{36}+\frac{20}{36}-\frac{15}{36}\)\(=\frac{29}{36}\)

\(\frac{2}{5}\times\frac{1}{4}:\frac{3}{8}=\frac{2\times1\times8}{5\times4\times3}=\frac{16}{60}=\frac{4}{15}\)

a) 2/3 + 5/9 = 11/9 - 3/4 = 17/36

b) 2/5 * 1/4 = 1/10 : 3/8 = 4/15

Mik cũng ko chắc nữa có sai thì cho mink sorry bạn nha

a) 2/3+5/9-3/4

=11/9-3/4

=17/36

b) 2/5x1/4:3/8

=1/10:3/8

=4/15

chúc bạn học tốt nha!!!!!

a) \(\dfrac{2}{5}\cdot\dfrac{1}{7}+\dfrac{2}{5}\cdot\dfrac{5}{7}+\dfrac{2}{5}\)

\(=\dfrac{2}{5}\left(\dfrac{1}{7}+\dfrac{5}{7}+1\right)\)

\(=\dfrac{2}{5}\cdot\dfrac{13}{7}=\dfrac{26}{35}\)

b) \(\dfrac{1}{5}+\dfrac{2}{8}+\dfrac{4}{5}+\dfrac{7}{8}-\dfrac{1}{8}\)

\(=\left(\dfrac{1}{5}+\dfrac{4}{5}\right)+\left(\dfrac{2}{8}+\dfrac{7}{8}-\dfrac{1}{8}\right)\)

\(=1+1=2\)

c)\(\dfrac{24}{36}\cdot\dfrac{10}{12}\cdot36\)

\(=\dfrac{24\cdot10\cdot36}{36\cdot12}=\dfrac{12\cdot2\cdot10\cdot36}{12\cdot36}\)

\(=2\cdot10=20\)

2/5x1/4:3/2

=2/20 : 3/2

=4/60=1/15

\(\dfrac{2}{5}\) x \(\dfrac{1}{4}:\dfrac{3}{2}=\dfrac{2}{20}:\dfrac{3}{2}=\dfrac{1}{10}:\dfrac{3}{2}=\dfrac{1}{10}\) x \(\dfrac{2}{3}=\dfrac{2}{30}\)
 

\(\dfrac{11}{3}-\dfrac{2}{3}\left(2\dfrac{2}{5}x\dfrac{1}{4}+0,2\right)\)

\(\Leftrightarrow3\left(\dfrac{12}{5}\times\dfrac{1}{4}+0,2\right)\)

\(\Leftrightarrow3\left(\dfrac{3}{5}+\dfrac{1}{5}\right)\)

\(\Leftrightarrow3\times\dfrac{4}{5}\)

\(\Leftrightarrow\dfrac{12}{5}\)

\(2\times3=6\)

\(8-4=4\)

\(4\times10=40\)

\(5\times1=5\)

\(2\times9=18\)

\(5\times2=10\)

2x3=6        8-4=4        4x10=40

5x1=5         2x9=18      5x2=10

2×3=6

8-4=4

5×1=5

2×9=18

5×2=10

  1/2x1/3+1/3x1/4+1/4x1/5+1/5x1/6+1/6x1/7+1/7x1/8+1/8x1/9

=7/18

`1/5xx1/2:3/10`

`=1/10xx10/3`

`=1/3`

`1/2xx1/3:1/4`

`=1/6xx4/1`

`=2/3`

a. \(\dfrac{1}{5}\times\dfrac{1}{2}:\dfrac{3}{10}=\dfrac{1}{10}:\dfrac{3}{10}=\dfrac{1}{10}\times\dfrac{10}{3}=\dfrac{10}{30}=\dfrac{1}{3}\)

b. \(\dfrac{1}{2}\times\dfrac{1}{3}:\dfrac{1}{4}=\dfrac{1}{6}:\dfrac{1}{4}=\dfrac{1}{6}\times\dfrac{4}{1}=\dfrac{4}{6}=\dfrac{2}{3}\)

a) \(\dfrac{1}{5}\times\dfrac{1}{2}:\dfrac{3}{10}=\dfrac{1}{5}\times\dfrac{1}{2}\times\dfrac{10}{3}=\dfrac{1\times1\times10}{5\times2\times3}=\dfrac{10}{30}=\dfrac{1}{3}\)

b) \(\dfrac{1}{2}\times\dfrac{1}{3}:\dfrac{1}{4}=\dfrac{1}{2}\times\dfrac{1}{3}\times4=\dfrac{1\times1\times4}{2\times3}=\dfrac{4}{6}=\dfrac{2}{3}\)