`1)`
`(x-3)/(5-x)=5/7` ĐK : `x ne 5`
`to 7(x-3)=5(5-x)`
`to 7x-21=25-5x`
`to 7x+5x=25+21`
`to 12x=46`
`to x=23/6 \ \ text{(tm)}`
Vậy `x=23/6`
`2)`
`(x-2)/(x-1)=(x+4)/(x+7)` ĐK : `x ne 1;-7`
`to (x-2)(x+7)=(x+4)(x-1)`
`to x^2+5x-14=x^2+3x-4`
`to x^2-x^2+5x-3x=-4+14`
`to 2x=10`
`to x=5 \ \ text{(tm)}`
Vậy `x=5`
`3)`
`0,52 : x = 9,63 : 16,38` ĐK : `x ne 0`
`to (0,52)/x = (9,63)/(16,38)`
`to (0,52)/x = 107/182`
`to 107x=182.0,52`
`to 107x=94,64`
`to x=2366/2675 \ \ text{(tm)}`
Vậy `x=2366/2675`
