a) \(\dfrac{3}{4}\times x:\dfrac{1}{2}=\dfrac{4}{5}\)

\(\dfrac{3}{4}\times x=\dfrac{4}{5}\times\dfrac{1}{2}\)

\(\dfrac{3}{4}\times x=\dfrac{2}{5}\)

\(x=\dfrac{2}{5}:\dfrac{3}{4}\)

\(x=\dfrac{8}{15}\)

b) \(\left(14-x:6\right)\times7=84\)

\(14-x:6=84:7\)

\(14-x:6=12\)

\(x:6=14-12\)

\(x:6=2\)

\(x=6\times2=12\)

c) \(x\times1,5:2,4=0,3\)

\(x\times1,5=0,3\times2,4\)

\(x\times1,5=0,72\)

\(x=0,72:1,5\)

\(x=0,48\)

d) Thiếu x

a \(\dfrac{3}{8}\times\dfrac{5}{2}+\dfrac{5}{8}\times\dfrac{5}{2}=\dfrac{5}{2}\left(\dfrac{3}{5}+\dfrac{5}{8}\right)=\dfrac{5}{2}\times\dfrac{8}{8}=\dfrac{5}{2}\times1=\dfrac{5}{2}\)

b \(33.12\times0=0\)

a) = (3/8 + 5,8) : 2/5 = 107/8 : 2/5 = 535/16

b) = 33,12 x 0 = 0

a 3/8 : 2/5 + 5,8 : 2/5

 3/8 x 5/2 + 5,8 x 5/2

= 5/2 x ( 3/8 + 5.8)

= 5/2 x  6,175

= 247/16

nếu chỗ 5,8 bn ghi sai thì mik sửa đề thành 3/8 : 2/5 + 5/8 : 2/5

3/8 x 5/2 + 5/8 x 5/2

=  5/2 x ( 3/8 + 5/8)

= 5/2 x 1

=5/2

b (13,8 x 2,4 ) x (2,25 - 1,5 x 1,5 )

= 33.12 x 0

= 0

a: =>1,2<x<2,4

=>x=2

b: =>2,76<x<3,51

=>x=3

A.  x - 3,5  =  2,4 + 1,5

              x  =  3,9 + 3,5

              x  =  7,4

B.  x + 6,14  =  27,8 - 8,6

               x  =  19,2 - 6,14 

                  x  = 12,8

C.  4,3 x  x  =  3,8 x 4,3

                x  =  3,8 x 4,3 : 4,3

                x  =  3,8

D.   7, 3 x x + 2,7 x x = 10

       x x ( 7, 3  + 2,7 ) = 10

                               x  = 10 : 10

                               x = 1

x – 3,5 = 2,4 + 1,5

x – 3, 5 = 3,9

x = 3,9 + 3,5

x = 7,4

\(a,5,2x+7\dfrac{2}{5}=6\dfrac{3}{4}\\ \Rightarrow\dfrac{26}{5}x+\dfrac{37}{5}=\dfrac{27}{4}\\ \Rightarrow\dfrac{26}{5}x=-\dfrac{13}{20}\\ \Rightarrow x=-\dfrac{1}{8}\\ b,2,4:\left(\dfrac{-1}{2}-x\right)=1\dfrac{3}{5}\\ \Rightarrow\dfrac{12}{5}:\left(\dfrac{-1}{2}-x\right)=\dfrac{8}{5}\\ \Rightarrow\dfrac{-1}{2}-x=\dfrac{3}{2}\\ \Rightarrow x=-2\)

a: x=2/3-4/5=10/15-12/15=-2/15

b: 1/2-x=7/12

=>x=1/2-7/12=-1/12

c: =>7/2:x=-7/2

=>x=-1

d: =>1/6x=3/8-5/2=3/8-20/8=-17/8

=>x=-17/8*6=-102/8=-51/4

e: =>1,5x=-1,5

=>x=-1

\(x+3^2=7-x\)

\(x+x=7-9\)

\(2x=-2\)

\(x=-1\)

\(2\left|x-1\right|-7=-3\)

\(2\left|x-1\right|=4\)

\(\left|x-1\right|=2\)

\(\orbr{\begin{cases}x-1=2\\x-1=-2\end{cases}}\)

\(\orbr{\begin{cases}x=3\\x=-1\end{cases}}\)

1) x + 3^2 = 7 - x

<=> x + 9 = 7 + (-x)

<=> x + 9 = -x + 7

<=> x + 9 + x = 7

<=> 2x + 9 = 7

<=> 2x = 7 - 9

<=> 2x = -2

<=> x = (-2) : 2

<=> x = -1

3) 2|x - 1| - 7 = -3

<=> 2|x - 1| = -3 + 7

<=> 2|x - 1| = 4

<=> |x - 1| = 4 : 2

<=> |x - 1| = 2

<=> x - 1 = -+2

<=> x - 1 = 2 hoặc x - 1 = -2

       x = 1 + 2         x = -2 + 1

      x = 3                x = -1

=> x = 3 hoặc x = -1