`a)(4,5-2x)*1 4/7=11/14`

`=>(4,5-2x)*11/7=11/14`

`=>4,5-2x=1/2`

`=>2x=4,5-0,5=4`

`=>x=2`

Vậy `x=2`

`b)(2,8x-32):2/3=-90`

`=>2,8x-32=-90*2/3=-60`

`=>2,8x=-28`

`=>x=-10`

Vậy `x=-10`

a) x=-10

b)x=2

a,    x=10

b,   x= 2

A/\(\left(2,8x-32\right):\frac{2}{3}=-90\)

\(\left(\frac{28}{10}x-32\right)=\frac{-90}{1}.\frac{2}{3}\)

\(\left(\frac{14}{5}x-32\right)=\frac{-30}{1}.\frac{2}{1}\)

\(\left(\frac{14}{5}x-32\right)=-60\)

\(\frac{14}{5}x=-60+32\)

\(\frac{14}{5}x=-28\)

\(x=\frac{-28}{1}:\frac{14}{5}\)

\(x=\frac{-28}{1}.\frac{5}{14}\)

\(x=\frac{-2}{1}.\frac{5}{1}=-10\)

B/\(\left(4,5-2x\right).1\frac{4}{7}=\frac{11}{14}\)

\(\left(\frac{45}{10}-2x\right).\frac{11}{7}=\frac{11}{14}\)

\(\left(\frac{9}{2}-2x\right)=\frac{11}{14}:\frac{11}{7}\)

\(\left(\frac{9}{2}-2x\right)=\frac{11}{14}.\frac{7}{11}\)

\(\left(\frac{9}{2}-2x\right)=\frac{1}{2}.\frac{1}{1}=\frac{1}{2}\)

\(2x=\frac{9}{2}-\frac{1}{2}\)

\(2x=\frac{8}{2}\)

\(x=\frac{8}{2}:\frac{2}{1}=\frac{8}{2}.\frac{1}{2}\)

\(x=\frac{4}{2}.\frac{1}{1}=\frac{4}{2}=2\)

a, \(\left(2,8x-32\right):\dfrac{2}{3}=-90\)

\(\Rightarrow2,8x-32=-60\)

\(\Rightarrow2,8x=-28\)

\(\Rightarrow x=-10\)

Vậy x = -10

b, \(\left(4,5-2x\right):1\dfrac{4}{7}=\dfrac{11}{14}\)

\(\Rightarrow\left(4,5-2x\right):\dfrac{11}{7}=\dfrac{11}{14}\)

\(\Rightarrow4,5-2x=\dfrac{121}{98}\)

\(\Rightarrow2x=\dfrac{160}{49}\)

\(\Rightarrow x=\dfrac{80}{49}\)

Vậy \(x=\dfrac{80}{49}\)

\(a,\left(2,8x-32\right):\dfrac{2}{3}=-90\)

\(2,8x-32=-90.\dfrac{2}{3}\)

\(2,8x-32=-60\)

\(2,8x=-60+32\)

\(2,8x=-28\)

\(x=-28:2,8\)

\(x=-10\)

Vậy \(x=-10\)

\(b,\left(4,5-2x\right):1\dfrac{4}{7}=\dfrac{11}{14}\)

\(\left(4,5-2x\right):\dfrac{11}{7}=\dfrac{11}{14}\)

\(4,5-2x=\dfrac{11}{14}.\dfrac{11}{7}\)

\(4,5-2x=\dfrac{121}{98}\)

\(2x=4,5-\dfrac{121}{98}\)

\(2x=\dfrac{160}{49}\)

\(x=\dfrac{160}{49}:2\)

\(x=\dfrac{80}{49}\)

Vậy \(x=\dfrac{80}{49}\)

\(a,\left(2,8x-32\right):\dfrac{2}{3}=-90\)

\(2,8x-32\) \(=-90.\dfrac{2}{3}\)

\(2,8x-32\)

\(\left(5+\frac{4}{7}\right):x=13\)

\(\frac{39}{7}:x=13\)

\(x=\frac{39}{7}:13\)

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

\(\left[5+\frac{4}{7}\right]:x=13\)

\(\Rightarrow\left[\frac{5\cdot7+4}{7}\right]:x=13\)

\(\Rightarrow\frac{39}{7}:x=13\)

\(\Rightarrow x=\frac{39}{7}:13=\frac{39}{7}\cdot\frac{1}{13}=\frac{3}{7}\cdot\frac{1}{1}=\frac{3}{7}\)

\(\left[2,8\cdot x+32\right]:\frac{2}{3}=90\)

\(\Rightarrow\left[2,8\cdot x+32\right]=90\cdot\frac{2}{3}\)

\(\Rightarrow\left[2,8\cdot x+32\right]=60\)

\(\Rightarrow2,8\cdot x+32=60\)

\(\Rightarrow2,8\cdot x=60-32\)

\(\Rightarrow2,8\cdot x=28\)

Đến đây dễ rồi :v

\(\left(2,8.x+32\right):\frac{2}{3}=90\)

\(2,8.x+32=90.\frac{2}{3}\)

\(2,8.x+32=60\)

\(2,8.x=60-32\)

\(2,8.x=28\)

\(x=28:2,8\)

\(x=10\)

giúp mình với

b,=-515phan14                          b,=2

trả loi theo thu tu luon giup mk

\(\left(2,8x-32\right)\div\frac{2}{3}=-90\)

\(\Rightarrow2,8x-32=-60\)

\(\Rightarrow2,8x=-28\)

\(\Rightarrow x=-10\)

\(\left(4,5-2x\right)\times1\frac{4}{7}=\frac{11}{14}\)

\(\Rightarrow4,5-2x=\frac{1}{2}\)

\(\Rightarrow2x=4\)

\(\Rightarrow x=2\)

\(a.\left(2,8x-32\right):\frac{2}{3}=-90\)

\(2,8x-32=-90\cdot\frac{2}{3}=-30\cdot\frac{2}{1}\)

\(2,8x-32=-60\)

\(2,8x=-60+32\)

\(2,8x=28\)

\(x=\frac{28}{2,8}=10\). Vậy x=10

\(b.\left(4,5-2x\right)\cdot1\frac{4}{7}=\frac{11}{14}\)

\(4,5-2x=\frac{11}{14}:\frac{11}{7}=\frac{11}{14}\cdot\frac{7}{11}\)

\(4,5-2x=\frac{1}{2}\)

\(2x=\frac{45}{10}-\frac{1}{2}=\frac{9}{2}-\frac{1}{2}=\frac{8}{2}\)

\(2x=4\)

\(x=\frac{4}{2}=2\) . Vậy x=2

Chúc bạn học tốt!^_^

a)(2,8x-32):\(\frac{2}{3}\)=-90

          (2,8x-32)  =(-90).\(\frac{2}{3}\)

          (2,8x-32)  =(-60)

                 2,8x   =(-60)+32

                 2,8x   =(-28)

                     x    =(-28):2,8

                     x    =(-10)

b)(4,5-2x).1\(\frac{4}{7}\)=\(\frac{11}{14}\)

   (4,5-2x).\(\frac{11}{7}\)=\(\frac{11}{14}\)

           (4,5-2x)    =\(\frac{11}{14}\):\(\frac{11}{7}\)

           (4,5-2x)    =\(\frac{1}{2}\)

                  2x    =4,5-\(\frac{1}{2}\)

                  2x    =4

                    x    =4:2

                    x    =2

tính trên máy tính casio được đấy

a)(2,8x-32):\(\frac{2}{3}\)=-90

2,8x-32=-90.\(\frac{2}{3}\)

2,8x      =-60+32

x          =-28:2,8

x=-10

b)(4,5-2x).1\(\frac{4}{7}\)=\(\frac{11}{14}\)

4,5-2x            =\(\frac{11}{14}:\frac{11}{7}\)

-2x                =\(\frac{1}{2}\)

x=-1/4