helppppp vs mik dang can rat gap

Bài `1`

`a)(-5)/12+3/8+(-7)/12+5/8+4/9`

`=((-5)/12+(-7)/12)+(3/8+5/8)+4/9`

`=(-12)/12+8/8+4/9`

`=-1+1+4/9`

`=0+4/9`

`=4/9`

`b)(-2)/5 . 5/13-2/5 . 8/13+2/5`

`=(-2)/5 .(5/13+8/13)+2/5`

`=(-2)/5 . 13/13+2/5`

`=(-2)/5 .1+2/5`

`=(-2)/5+2/5`

`=0/5`

`=0`

Bài `2`

`a)5/7-3/7x=1`

`<=>3/7x=5/7-1`

`<=>3/7x=5/7-7/7`

`<=>3/7x=(-2)/7`

`<=>x=(-2)/7:3/7`

`<=>x=(-2)/7 . 7/3`

`<=>x=(-2)/3`

Vậy `x=(-2)/3`

`b)1/4+3/5:(2x-1)=1`

`<=>3/5:(2x-1)=1-1/4`

`<=>3/5:(2x-1)=4/4-1/4`

`<=>3/5:(2x-1)=3/4`

`<=>2x-1=3/5:3/4`

`<=>2x-1=3/5 . 4/3`

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

`<=>2x=4/5+1`

`<=>2x=4/5+5/5`

`<=>2x=9/5`

`<=>x=9/5:2`

`<=>x=9/5 . 1/2`

`<=>x=9/10`

Vậy `x=9/10`