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

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

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

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

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

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

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

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

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

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

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

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

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

\(2,8x=28\)

\(x=\frac{28}{2,8}=10\). 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

giúp mình với

b,=-515phan14                          b,=2

trả loi theo thu tu luon giup mk

\(\left(2.8x-32\right):\frac{2}{3}=90\)

\(2.8\cdot x-32=90\cdot\frac{2}{3}\)

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

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

\(\frac{14}{5}x=92\)

\(x=\frac{230}{7}\)

B , c , d tương tự

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

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

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

\(\Rightarrow x=-10\)

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

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

\(\Rightarrow2x=4\)

\(\Rightarrow x=2\)

a) x=-10

b)x=2

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

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

\(2,8x=-28\)

\(x=-10\)

Vậy x = -10

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

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

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

\(2x=4\)

\(x=2\)

Vây x = 2

a) 2/3 x = 2/9 + 4/9

=> 2/3 x = 2/3

=> x = 1

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

=> 4,5 - 2x = 5/14

=> 2x = 4,5 - 5/14

=> 2x = 29/7

=> x= 29/14