`x/5 = 2/5`
`⇒x = 2`
`3/8 = 6/x`
`⇔3x/8x=48/8x`
`⇒3x=48`
`⇔x=16`
`1/9=x/27`
`⇔3/27=x/27`
`⇒x=3`
`\frac{3}{x-5}=\frac{-4}{x+2}`
`⇔\frac{3(x+2)}{(x-5)(x+2)}=\frac{-4(x-5)}{(x-5)(x+2)}`
`⇒3(x+2)=-4(x-5)`
`⇔3x+6=-4x+20`
`⇔7x=14`
`⇔x=2`
`x/-2=-8/x`
`⇔-x/2=-8/x`
`⇔-x^2/2x=-16/2x`
`⇔-x^2=-16`
`⇔x^2=16`
`⇔x=±4`