-12-(-28) = 16

Ta thay x = -28 vào biểu thức ( - 12 ) - x ta có:

( -12 ) - ( -28) = ( -12 ) + 28 = 16

\(\dfrac{-4}{50}\text{=}\dfrac{-2}{25}\)

\(\dfrac{6}{25}\text{=}\dfrac{6}{25}\)

\(\dfrac{-27}{54}\text{=}\dfrac{-1}{2}\)

\(\dfrac{-18}{-75}\text{=}\dfrac{6}{25}\)

\(\dfrac{28}{-56}\text{=}-\dfrac{1}{2}\)

suy ra chỉ có phân số \(\dfrac{-4}{50}\) là không bằng phân số nào trong các phân số còn lại

-1/2

a, 10 -12 - 8

= 10 - (12 + 8 )

= 10 - 20 = -10

b, 4-(-15)-5+6

= 4+15-5+6

= (4+6) + (15-5)

= 10+10=20

c, 2-12-4-6

= (2-12)-(4+6)

= (-10) - 10

=-20

d, -45-5-(-12)+8

= -45-5+12+8

= [(-45)-5]+(12+8)

= (-50)+20

= -30

\(a.10-12-8\\ =10+\left(-12-8\right)\\ =10+\left(-20\right)=-10\\ b.4-\left(-15\right)-5+6\\ =4+5-5+6\\ =\left(4+6\right)+\left(15-5\right)\\ =10+10=20\\ c.2-12-4-6\\ =\left(2-12\right)+\left(-4-6\right)\\ =-10+\left(-10\right)=-20\\ d.-45-5-\left(-12\right)+8\\ =-45-5+12+8\\ =\left(-45-5\right)+\left(12+8\right)\\ =-50+20=-30\)

`2.x-49=5.9`

`=> 2.x-49=45`

`=>2.x=45+49`

`=>2.x=94`

`=>x=94:2`

`=>x=47`

2 . x - 49 = 45 

2 . x = 49 + 45 

2 . x = 94 

   x = 94 : 2

  x = 47

`(3x+35):2-16=18.5`

`(3x+35):2-16=90`

`(3x+35):2=90+16=106`

\(3x+35=106\times2=212\)

`3x=212-35`

`3x=177`

`x=177:3`

`x=59`

\(\left(3x+35\right):2-16=18\cdot5\\ \left(3x+35\right):2-16=90\\ \left(3x+35\right):2=90+16\\ \left(3x+35\right):2=106\\ \left(3x+35\right)=106\cdot2\\ \left(3x+35\right)=212\\ 3x=212-35\\ 3x=177\\ x=177:3\\ x=59\)

\(=>x-9=77:11\\ =>x-9=7\\ =>x=7+9\\ =>x=16\)

\(11\cdot\left(x-9\right)=77\\ \left(x-9\right)=77:11\\ \left(x-9\right)=7\\ x=7+9\\ x=16\)

`5.(x-9)=350`

`x-9=350:5`

`x-9=70`

`x=70+9`

`x=79`

\(=>x-9=350:5\\ =>x-9=70\\ =>x=70+9\\ =>x=79\)

\(=>x+41=400:4\\ =>x+41=100\\ =>x=100-41\\ =>x=59\)

`4.(x+41)=400`

`x+41=400:4`

`x+41=100`

`x=100-41`

`x=59`

140:(x-8)=7

x-8=140:7

x-8=20

x=20+8

x=28

140:(x-8)=7

x-8=140:7

x-8=20

   x=20+8

   x=28

\(=>x+4=198-120\\ =>x+4=78\\ =>x=78-4\\ =>x=74\)

74