Certified GKH Gardening Expert
I believe our expert is suggesting that if you use one cup of salt, add it to 3 cups of water - not weight, but volume. Don't forget that for a few pesky weeds on the driveway, boiling water will do the job.
Here's an extension service article that compares homemade weed killers to glyphosate: https://www.ag.ndsu.edu/cpr/weeds/homemade-herbicide-08-28-14
and another one of ours that may help: https://www.gardeningknowhow.com/plant-problems/weeds/weeds-in-tight-spaces.htm