Übersicht

`3/4 = 1/4 b + 3 || -12/4 ` (= 3)

`-9/4 = 1/4 b || *4 `

`-9 = b `

Probe:

`3/4 = 1/4 *(-9) + 3 `

`3/4 = -9/4 + 12/4 `

`3/4 = 3/4 ` ✔✔

`=> L={-9} `