From its name of 18 carat gold you can tell, if it is truly 18 carat gold, that there is 18/24ths gold and 6/24ths of another metal, possibly copper or platinum. 18 carat gold is (18/24)x100= 75%...
Very tricky! No, 24 Carat gold is not pure gold, but a diamond of that weight would be impressive indeed. Carat with a 'C' is a weight measure used for gemstones. Karat with a K, as you will see...
14/24 or about 0.583 It would be 0.583 if it was a ratio, but it isn't. It's however, a percent. You forgot, one important step. To either, multiply by 100, or, move the decimal twice. 14/24 = .0583...