Giúp e vs các ac ưiiiiiiii

Đáp án +Giải thích các bước giải

6)`45,65xx72+28xx45,65-5,65xx65-5,65xx35`

`=45,65xx(72+28)-5,65xx(65+35)`

`=45,65xx100-5,65xx100`

`=100xx(45,65-5,65)`

`=100xx40`

`=4000`

7)a) `(x-1/2)xx5/2+1/2=7/4`

`<=>(x-1/2)xx5/2=7/4-1/2`

`<=>(x-1/2)xx5/2=5/4`

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

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

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

`<=>x=2/2`

`<=>x=1`

Vậy `x=1`

b) `75% xx x+3/4 xx x-x=30`

`<=>x xx(75%+3/4-1)=30`

`<=>x xx(3/4+3/4-1)=30`

`<=>x xx1/2=30`

`<=>x=30:1/2`

`<=>x=60`

Vậy `x=60`