`(3/5.x+7/10) : 2^2 = (-1)/12`
`<=> (3/5.x + 7/10) : 4 = (-1)/12`
`<=> 3/5.x + 7/10 = (-1)/12 . 4`
`<=> 3/5.x + 7/10 = (-1)/3`
`<=> 3/5.x + = (-1)/3 - 7/10`
`<=> 3/5.x = (-10)/30 - 21/30`
`<=> 3/5.x = (-31)/30`
`<=> x = (-31)/30 :3/5`
`<=> x = (-31)/30 . 5/3`
`<=> x = (-31)/18`