53,2 : ( `x` - `3,5` )+ `45,8` = `99`
53,2 : ( `x` - `3,5` ) = `99` - `45,8`
53,2 : ( `x` - `3,5` ) = `53,2`
( `x` - `3,5` ) = `53,2` : `53,2`
`x` - `3,5` = `1`
`x` = `1` + `3,5`
`x` = `4,5`
b)
`6/5` + `4,2` x `x` = `13,8`
`1,2` + `4,2` x `x` = `13,8`
`4,2` x `x` = `13,8` - `1,2`
`4,2` x `x` = `12,6`
`x` = `12,6` : `4,2`
`x` = `3`