dandelions or any deep rooted perennial weeds
eg couch grass, bind weed, creeping thistle there is only one solution
as smiffy said Glyphosate
beware it comes in different strengths and you can pay top dollar for piss,
builders merchants, agrochemical merchants etc in gallon containers, not cheap but …
and, if you want cheap … boiling water
salt water will will not be absorbed it will cause dehydration
……………..osmosis anyone?