\(\dfrac{1}{2}\times\dfrac{1}{3}+\dfrac{2}{3}+\dfrac{1}{2}\)
\(=\dfrac{1}{6}+\dfrac{2}{3}+\dfrac{1}{2}\)
\(=\dfrac{1}{6}+\dfrac{4}{6}+\dfrac{3}{6}\)
\(=\dfrac{8}{6}=\dfrac{4}{3}\)

\(x-\dfrac{1}{3}=\dfrac{2}{3}.\dfrac{9}{14}+\dfrac{3}{7}\)

\(x-\dfrac{1}{3}=\dfrac{1}{7}+\dfrac{3}{7}\)

\(x-\dfrac{1}{3}=\dfrac{4}{7}\)

\(x=\dfrac{19}{21}\)

x = 19/21 nha

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

`=1/10xx10/3`

`=1/3`

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

`=1/6xx4/1`

`=2/3`

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

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

\(\left(\frac{5}{12}+\frac{1}{2}.\frac{1}{3}\right):\left(2.\frac{1}{3}-1.\frac{5}{12}\right)\)

\(=\left(\frac{5}{12}+\frac{1}{6}\right):\left(\frac{2}{3}-\frac{5}{12}\right)\)

\(=\frac{7}{12}:\frac{1}{4}\)

\(=\frac{7}{3}\)

_Chúc bạn học tốt_

Đề bài 

= ( 5/12 +    1/6 ) : (    2/3 - 1/12 ) 

= ( 5/12 + 2/12 ) :   ( 8/12 - 1/12 ) 

= 7/12 : 7/12 

= 1 

K Trắng nha .

=1 nha

\(\left(\frac{5}{12}+\frac{1}{2}\times\frac{1}{3}\right):\left(2\times\frac{1}{3}-1\times\frac{1}{12}\right)\)

\(=\left(\frac{5}{12}+\frac{1}{6}\right):\left(\frac{2}{3}-\frac{1}{12}\right)\)

\(=\frac{7}{12}:\frac{7}{12}\)

\(=1\)

k bk tính nhanh!

1234567890

Lần sau nhớ chọn đúng môn

Uk, Long cứ đợi ng ta trả lời xong long làm giống là đc ý mà!

Sửa đề: \(\frac12\cdot1+\frac13\left(1+2\right)+\frac14\left(1+2+3\right)+\cdots+\frac{1}{100}\left(1+2+3+\cdots+99\right)\)

\(=\frac12+\frac13\cdot\frac{2\cdot3}{2}+\frac14\cdot\frac{3\cdot4}{2}+\cdots+\frac{1}{100}\cdot\frac{99\cdot100}{2}\)

\(=\frac12+\frac22+\frac32+\cdots+\frac{99}{2}=\frac12\left(1+2+\cdots+99\right)\)

\(=\frac12\cdot99\cdot\frac{\left(99+1\right)}{2}=\frac12\cdot99\cdot50=25\cdot99=2475\)

đề??

Chắc là tính ắ;vv