`x xx 6/7=5/14`

`=>x=5/14:6/7`

`=>x=5/14xx7/6`

`=>x=35/84`

`=>x=5/12`

Vậy `x=5/12`

__

`x:2/3=4/9`

`=>x=4/9xx2/3`

`=>x=8/27`

Vậy `x=8/27`

__

`x-1/4=3/2`

`=>x=3/2+1/4`

`=>x=6/4+1/4`

`=>x=7/4`

Vậy `x=7/4`

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`x+4/5=8/9`

`=>x=8/9-4/5`

`=>x=40/45-36/45`

`=>x=4/45`

Vậy `x=4/45`

\(x\cdot\dfrac{6}{7}=\dfrac{5}{14}\)

\(x\)         \(=\dfrac{5}{14}:\dfrac{6}{7}\)

\(x\)           \(=\dfrac{5}{12}\)

\(x:\dfrac{2}{3}=\dfrac{4}{9}\)

\(x\)        \(=\dfrac{4}{9}\cdot\dfrac{2}{3}\)

\(x\)          \(=\dfrac{8}{27}\)

\(x-\dfrac{1}{4}=\dfrac{3}{2}\)

\(x\)          \(=\dfrac{3}{2}+\dfrac{1}{4}\)

\(x\)            \(=\dfrac{7}{4}\)

\(x+\dfrac{4}{5}=\dfrac{8}{9}\)

\(x\)          \(=\dfrac{8}{9}-\dfrac{4}{5}\)

\(x\)            \(=\dfrac{4}{45}\)

1.viết số thích hợp

3 tạ=30yến                              1/4 giờ=15phút            

360 giây=6phút                      10 thế kỉ=1000năm

4km²  400m² =40400m²                  800cm²=8dm²

bài 2 đâu

II . Tự luận 

`1)a)7/15+4/5`

`=7/15+(4xx3)/(5xx3)`

`=7/15+12/15`

`=19/15`

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`b)4/5 xx 5/8` 

`=(4xx5)/(5xx8)`

`=4/8`

`=1/2`

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`c)2/3-3/8`

`=16/24-9/24`

`=7/24`

__

`d)1/2:2/5`

`=1/2xx5/2`

`=(1xx5)/(2xx2)`

`=5/4`

M

a: \(=\dfrac{1}{2}\cdot\dfrac{3}{4}\cdot\dfrac{5}{6}=\dfrac{15}{48}=\dfrac{5}{16}\)

b: \(=\dfrac{2}{3}+\dfrac{12}{42}=\dfrac{2}{3}+\dfrac{2}{7}=\dfrac{20}{21}\)

c: \(=\dfrac{24}{5}\cdot\dfrac{5}{12}=2\)

d: \(=\dfrac{1}{9}+\dfrac{3}{4}=\dfrac{4+27}{36}=\dfrac{31}{36}\)

1.\(\dfrac{11}{18};\dfrac{7}{9};\dfrac{14}{15}\)

2.\(\dfrac{4}{9}+\dfrac{3}{7}=\dfrac{28}{63}+\dfrac{27}{63}=\dfrac{55}{63}\)

\(\dfrac{5}{6}-\dfrac{3}{8}=\dfrac{20}{24}-\dfrac{9}{24}=\dfrac{11}{24}\)

\(\dfrac{18}{25}\cdot\dfrac{15}{6}=\dfrac{18\cdot15}{25\cdot6}=\dfrac{270}{150}=\dfrac{9}{5}\)

\(\dfrac{30}{49}:\dfrac{6}{7}=\dfrac{30}{49}\cdot\dfrac{7}{6}=\dfrac{30\cdot7}{49\cdot6}=\dfrac{210}{294}=\dfrac{5}{7}\)

2:

a: =28/63+27/63=55/63

b: =20/24-9/24=11/24

c: =270/150=9/5

d: \(=\dfrac{30}{49}\cdot\dfrac{7}{6}=\dfrac{1}{7}\cdot5=\dfrac{5}{7}\)

đáp án là c nha

35 nhé

\(\dfrac{5}{6}\) = \(\dfrac{5\times3}{6\times3}\) = \(\dfrac{15}{18}\)

Chọn B. \(\dfrac{15}{18}\)

đáp án là b nha

Diện tích hình bình hành là:

6 x 4 = 24 (cm²)

Chọn C. 24 cm²

Diện tích hình bình hành là:

6 x 4 = 24 (cm2)

         đ/s:24 cm2

 C. 24 cm2

A. \(\dfrac{9}{8}\)

a) 9/8 nha