a: 86-x>86-4

=>-x>-4

hay x<4

b: x+28<28+3

=>x+28<31

hay x<3

x=0,1,2,3

x=0,1,2

a,86-x>86-4

86-x > 82

-x > 82 -86

-x> -4

x< 4

b,x+28<28+3

x+ 28 < 31

=> x < 31 - 28 

x < 3

Bài 2: 

a: =>-5x=-200

hay x=40

b: =>x*2/3=1244

hay x=1866

Đề bài 1 sai rồi bạn

\(a,86-\left(86+x\right)=10\\ \Rightarrow86+x=76\\ \Rightarrow x=10\\ b,10-x=7-\left(-8\right)\\ \Rightarrow10-x=15\\ \Rightarrow x=-5\\ c,\left(-24+x\right)-43=15\\ \Rightarrow x-24=58\\ \Rightarrow x=82\)

\(37\times46+37\times51+111\)

\(=37\times46+37\times51+37\times3\)

\(=37\times\left(46+51+3\right)\)

\(=37\times100\)

\(=3700\)

------------

\(172\times47+86\times8-34\times4\)

\(=172\times47+172\times4-34\times4\)

\(=172\times\left(47+4\right)-34\times4\)

\(=172\times51-34\times4\)

\(=172\times3\times17-17\times2\times4\)

\(=17\times\left(172\times3-2\times4\right)\)

\(=17\times\left(516-8\right)\)

\(=17\times508\)

\(=8636\)

------------

\(35\times215-35\times200-175\)

\(=35\times215-35\times200-35\times5\)

\(=35\times\left(215-200-5\right)\)

\(=35\times10\)

\(=350\)

------------

\(48\times56+28\times104\)

\(=48\times2\times28+28\times104\)

\(=28\times\left(48\times2+104\right)\)

\(=28\times200\)

\(=5600\)

88 800

261 304

không phải nhé

8. Find the value of 14 x 14 + 2 x 14 x 86 + 86 x 86.

\(=\left(14\times3\right)+\left(86\times3\right)+2\)

\(=42+258+2\)

\(=300+2\)

\(=302\)

14 x 14 + 2 x 14 x 86 + 86 x 86 

= 14 x 14 + 14 x 86 + 14 x 86 + 86 x 86 

= 14 x ( 14 + 86 ) + 86 x ( 14 + 86 ) 

= 14 x 100 + 86 x 100 

= 100 x ( 14 + 86 ) 

= 100 x 100 

= 10000 

x + 86 = 144    

x = 144 - 86

x =  58                                                             

\(\Rightarrow x\times\left(56-46\right)=32250\\ \Rightarrow x\times10=32250\\ \Rightarrow x=3225\)

\(x\times56-x\times46=375\times86\\ \Rightarrow x\times\left(56-46\right)=32250\\ \Rightarrow x\times10=32250\\ \Rightarrow x=3225\)

\(x\times56-x\times46=375\times86\)

   \(x\times\left(56-46\right)=32250\)

              \(x\times10=32250\)

                       \(x=3225\)

a, \(\left(\dfrac{1}{2}+\dfrac{4}{7}\right):x=\dfrac{-3}{4}\)

\(\dfrac{15}{14}:x=\dfrac{-3}{4}\)

=> x= \(\dfrac{-7}{10}\)

b, 0,5:x-\(1\dfrac{3}{4}\)= 25%

0,5:x-\(\dfrac{7}{4}=\dfrac{1}{4}\)

0,5:x = 2

=> x = \(\dfrac{1}{4}\)