First of all op cows are herbivores.Secondly no support and last but not the least uninstall. jk don't uninstall
This only makes sense when said. What you typed made no sense and there was no answer. Those who knew remembered the viral videos which you took this riddle from, and applied that answer to this. When said aloud, the 8 can be replaced with "ate". SO it's saying that there were 30 cows, and 20 ate chickens. So the number of cows who didn't is 10.