X+\(\dfrac{2}{7}\)=\(\dfrac{1}{2}\)

X     = \(\dfrac{1}{2}\)-\(\dfrac{2}{7}\)
X     = \(\dfrac{3}{14}\)
Chọn đáp án A. \(\dfrac{3}{14}\)

A

`7 xx 3/14 -1/14`

`= 21/14 -1/14`

`= 20/14`

`=10/7`

__

`3/2 + 7/4 xx 2/5`

`= 3/2 + 14/20`

`= 3/2 + 7/10`

`= 15/10 +7/10`

`= 23/10`

__

`9/8 : 3 + 7/3 : 3`

`= 9/8 xx 1/3 + 7/3 xx 1/3`

`=1/3 xx ( 9/8 + 7/3)`

`= 1/3 xx 83/24`

`= 83/72`

__

`2 : 3/4 - 5/8 xx 4/3`

`= 2 xx 4/3 - 5/8 xx 4/3`

`= 4/3 xx ( 2-5/8)`

`= 4/3 xx ( 16/8 -5/8)`

`= 4/3 xx 11/8`

`= 44/24`

`=11/6`

` @ \color{Red}{sushiteam}`

Bài 1: 

a: -8/12<0<-3/-4

b: -56/24<0<7/3

c: 4/25<1<15/13

=>-4/25>-15/13

Bài 2: 

a: =-60/45=-4/3

b: =4/15-3/2-8/5=8/30-45/30-48/30=-85/30=-17/6

9/5 : 7/4 + 3/4 x 8/7       

= (9/5 : 8/7) x (7/4 + 3/4)

= 63/40 x 5/2

= 63/16

7 x 3/14 - 1/14

= 3/2 - 1/4

= 5/4

_{^{\(\dfrac{9}{5}:\dfrac{7}{4}+\dfrac{3}{4}\times\dfrac{8}{7}\)}}

_{^{\(=\dfrac{9}{5}\times\dfrac{4}{7}+\dfrac{3}{4}\times\dfrac{8}{7}\)}}

_{^{\(=\dfrac{36}{35}+\dfrac{6}{7}\)}}

_{^{\(=\dfrac{66}{35}\)}}

_{^{\(7\times\dfrac{3}{14}-\dfrac{1}{14}\)}}

_{^{\(=\dfrac{3}{2}-\dfrac{1}{14}\)}}

_{^{\(=\dfrac{10}{7}\)}}

\(\frac{1}{2}\cdot\frac{18}{14}+\frac{1}{2}\cdot\frac{3}{14}-\frac{1}{2}\cdot\frac{7}{14}\)

\(=\frac{1}{2}\left(\frac{18}{14}+\frac{3}{14}-\frac{7}{14}\right)\)

\(=\frac{1}{2}\cdot1=\frac{1}{2}\)

a/ 25/14

b/28

a) x + 3/5 = -1/15

=> x = -1/15 - 3/5

=> x = -2/3

b) x/14 = 1/7 - 3/14

=> x/14 = -1/14

=> x = -1

c) -1/2x + 1/5 = 3/10

=> -1/2x = 3/10 - 1/5

=> -1/2x = 1/5

=> x = 1/5 : (-1/2)

=> x = -2/5

d) 4/5 - (2/15 + x) = 1/15

=> 4/5 - 2/15 - x = 1/15

=> 2/3 - x = 1/15

=> x = 2/3 - 1/15

=> x = 3/5

D