`a,` `(x+7):1/3=12:(x+7)` `(` ĐKXĐ: `x ne 7``)`

`<=>3(x+7)=12/(x+7)`

`<=>3(x+7)^2=12`

`<=>(x+7)^2=4`

`<=>`  \(\left[ \begin{array}{l}x+7=2\\x+7=-2\end{array} \right.\) 

`<=>`  \(\left[ \begin{array}{l}x=-5\\x=-9\end{array} \right.\)  `(` TMĐK `)`

Vậy `x\in{-5;-9}`

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`c.` `(2x-3)/(3x-5)=3/8`  `(` ĐKXĐ: `x ne 5/3``)`

`<=>8(2x-3)=3(3x-5)`

`<=>16x-24=9x-15`

`<=>7x=9`

`<=>x=9/7` `(` TMĐK `)`

Vậy `x=9/7`