Giúp làm đề 5 bài 1 với bài 2

`1)`

`a)28/5:-7`

`=28/5 : {-1}/7`

`=-28/35`

`=-4/5`

`b)(3/8-1/4):1 3/8`

`=(3/8-2/8):11/8`

`=1/8 . 8/11`

`=8/88`

`=1/11`

`c)75%-(1,25-2 3/4):2/9`

`=3/4-(5/4-11/4) . 9/2`

`=3/4 - {-6}/4 . 9/2`

`=3/4 + 54/8`

`=3/4+27/4`

`=30/4`

`=15/2`

`d)1/3 . 3/4 +2/3 . 6/5 -1/3`

`=1/3(3/4-1)+12/15`

`=1/3 . {-1}/4 + 4/5`

`={-1}/12 + 4/5`

`={-5}/60+48/60`

`=43/60`

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`2)`

`a)x-2/3=1/2`

`x=1/2+2/3`

`x=3/6+4/6`

`x=7/6`

`-` Vậy : `x=7/6 .`

`b)2/9-7/8x=1/3`

`7/8x=2/9-3/9`

`7/8x=-1/9`

`x=-1/9:7/8`

`x=-1/9 . 8/7`

`x=-8/63`

`-` Vậy : `x=-8/63`

`c)(x-2/15). 9/25 = {-6}/25`

`x-2/15={-6}/25:9/25`

`x-2/15={-6}/9`

`x-2/15=-2/3`

`x=-2/3+2/15`

`x=-10/15+2/15`

`x=-8/15`

`-` Vậy : `x=-8/15`

`d)x/45={-6}/15`

`x/45={-18}/45`

`x=-18`

`-` Vậy : `x=-18.`

`#Sal_tSea`